Wrong colors in xterm

Question

I don't quite understand XTerm's (UXTerm's in this case) behaviour regarding colors. I'm using Solarized Light color theme for Alacritty and UXTerm. They're more or less identical:

~/.alacritty.yml:

# Colors (Solarized Light)
colors:
  # Default colors
  primary:
    background: '0xfdf6e3'
    foreground: '0x586e75'

  # Normal colors
  normal:
    black:   '0x073642'
    red:     '0xdc322f'
    green:   '0x859900'
    yellow:  '0xb58900'
    blue:    '0x268bd2'
    magenta: '0xd33682'
    cyan:    '0x2aa198'
    white:   '0xeee8d5'

  # Bright colors
  bright:
    black:   '0x002b36'
    red:     '0xcb4b16'
    green:   '0x586e75'
    yellow:  '0x657b83'
    blue:    '0x839496'
    magenta: '0x6c71c4'
    cyan:    '0x93a1a1'
    white:   '0xfdf6e3'

~/.Xresources:

#define S_base03        #002b36
#define S_base02        #073642
#define S_base01        #586e75
#define S_base00        #657b83
#define S_base0         #839496
#define S_base1         #93a1a1
#define S_base2         #eee8d5
#define S_base3         #fdf6e3
#define S_yellow        #b58900
#define S_orange        #cb4b16
#define S_red           #dc322f
#define S_magenta       #d33682
#define S_violet        #6c71c4
#define S_blue          #268bd2
#define S_cyan          #2aa198
#define S_green         #859900

!fonts&stuff
UXTerm*faceSize: 11
uxterm*eightBitInput: false
UXTerm*faceName: Fira Mono Regular

!Background & foreground
UXTerm*background: S_base3
UXTerm*foreground: S_base00
UXTerm*fading: 40
UXTerm*fadeColor: S_base3
UXTerm*cursorColor: S_base01
UXTerm*pointerColorBackground: S_base1
UXTerm*pointerColorForeground: S_base01

!UXTerm*borderColor: #343434

!Turning off scrollbar
UXTerm*scrollBar:  off

!Starting up with a geometry
UXTerm*vt100*geometry:   160x50

!Colors
!-------------------------
!black
UXTerm*color0: S_base02
UXTerm*color8: S_base03

!red
UXTerm*color1: S_red
UXTerm*color9: S_orange

!green
UXTerm*color2: S_green
UXTerm*color10: S_base01

!yellow
UXTerm*color3: S_yellow
UXTerm*color11: S_base00

!blue
UXTerm*color4: S_blue
UXTerm*color12: S_base0

!magenta
UXTerm*color5: S_magenta
UXTerm*color13: S_violet

!cyan
UXTerm*color6: S_cyan
UXTerm*color14: S_base1

!white
UXTerm*color7: S_base2
UXTerm*color15: S_base3

Alacritty session:

trueneu@pop-os:~$ env | grep TERM
COLORTERM=truecolor
TERM=xterm-256color

UXTerm session:

trueneu@pop-os:~$ env | grep TERM
COLORTERM=truecolor
XTERM_VERSION=XTerm(353)
XTERM_SHELL=/bin/bash
XTERM_LOCALE=en_US.UTF-8
TERM=xterm-256color

But they show completely different behaviours color-wise:

Alacritty:

UXTerm:

Though all is fine in emacs:

Alacritty:

UXTerm:

Both pass this test I've found:

#!/usr/bin/env bash

awk 'BEGIN{
    s="/\\/\\/\\/\\/\\"; s=s s s s s s s s;
    for (colnum = 0; colnum<77; colnum++) {
        r = 255-(colnum*255/76);
        g = (colnum*510/76);
        b = (colnum*255/76);
        if (g>255) g = 510-g;
        printf "\033[48;2;%d;%d;%dm", r,g,b;
        printf "\033[38;2;%d;%d;%dm", 255-r,255-g,255-b;
        printf "%s\033[0m", substr(s,colnum+1,1);
    }
    printf "\n";
}'

Alacritty:

UXTerm:

The prompt:

PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

Same with ls colors.

UXTerm's infocmp, if it helps:

    Reconstructed via infocmp from file: /lib/terminfo/x/xterm-256color
xterm-256color|xterm with 256 colors,
    am, bce, ccc, km, mc5i, mir, msgr, npc, xenl,
    colors#0x100, cols#80, it#8, lines#24, pairs#0x10000,
    acsc=``aaffggiijjkkllmmnnooppqqrrssttuuvvwwxxyyzz{{||}}~~,
    bel=^G, blink=\E[5m, bold=\E[1m, cbt=\E[Z, civis=\E[?25l,
    clear=\E[H\E[2J, cnorm=\E[?12l\E[?25h, cr=\r,
    csr=\E[%i%p1%d;%p2%dr, cub=\E[%p1%dD, cub1=^H,
    cud=\E[%p1%dB, cud1=\n, cuf=\E[%p1%dC, cuf1=\E[C,
    cup=\E[%i%p1%d;%p2%dH, cuu=\E[%p1%dA, cuu1=\E[A,
    cvvis=\E[?12;25h, dch=\E[%p1%dP, dch1=\E[P, dim=\E[2m,
    dl=\E[%p1%dM, dl1=\E[M, ech=\E[%p1%dX, ed=\E[J, el=\E[K,
    el1=\E[1K, flash=\E[?5h$<100/>\E[?5l, home=\E[H,
    hpa=\E[%i%p1%dG, ht=^I, hts=\EH, ich=\E[%p1%d@,
    il=\E[%p1%dL, il1=\E[L, ind=\n, indn=\E[%p1%dS,
    initc=\E]4;%p1%d;rgb\:%p2%{255}%*%{1000}%/%2.2X/%p3%{255}%*%{1000}%/%2.2X/%p4%{255}%*%{1000}%/%2.2X\E\\,
    invis=\E[8m, is2=\E[!p\E[?3;4l\E[4l\E>, kDC=\E[3;2~,
    kEND=\E[1;2F, kHOM=\E[1;2H, kIC=\E[2;2~, kLFT=\E[1;2D,
    kNXT=\E[6;2~, kPRV=\E[5;2~, kRIT=\E[1;2C, kb2=\EOE, kbs=^?,
    kcbt=\E[Z, kcub1=\EOD, kcud1=\EOB, kcuf1=\EOC, kcuu1=\EOA,
    kdch1=\E[3~, kend=\EOF, kent=\EOM, kf1=\EOP, kf10=\E[21~,
    kf11=\E[23~, kf12=\E[24~, kf13=\E[1;2P, kf14=\E[1;2Q,
    kf15=\E[1;2R, kf16=\E[1;2S, kf17=\E[15;2~, kf18=\E[17;2~,
    kf19=\E[18;2~, kf2=\EOQ, kf20=\E[19;2~, kf21=\E[20;2~,
    kf22=\E[21;2~, kf23=\E[23;2~, kf24=\E[24;2~,
    kf25=\E[1;5P, kf26=\E[1;5Q, kf27=\E[1;5R, kf28=\E[1;5S,
    kf29=\E[15;5~, kf3=\EOR, kf30=\E[17;5~, kf31=\E[18;5~,
    kf32=\E[19;5~, kf33=\E[20;5~, kf34=\E[21;5~,
    kf35=\E[23;5~, kf36=\E[24;5~, kf37=\E[1;6P, kf38=\E[1;6Q,
    kf39=\E[1;6R, kf4=\EOS, kf40=\E[1;6S, kf41=\E[15;6~,
    kf42=\E[17;6~, kf43=\E[18;6~, kf44=\E[19;6~,
    kf45=\E[20;6~, kf46=\E[21;6~, kf47=\E[23;6~,
    kf48=\E[24;6~, kf49=\E[1;3P, kf5=\E[15~, kf50=\E[1;3Q,
    kf51=\E[1;3R, kf52=\E[1;3S, kf53=\E[15;3~, kf54=\E[17;3~,
    kf55=\E[18;3~, kf56=\E[19;3~, kf57=\E[20;3~,
    kf58=\E[21;3~, kf59=\E[23;3~, kf6=\E[17~, kf60=\E[24;3~,
    kf61=\E[1;4P, kf62=\E[1;4Q, kf63=\E[1;4R, kf7=\E[18~,
    kf8=\E[19~, kf9=\E[20~, khome=\EOH, kich1=\E[2~,
    kind=\E[1;2B, kmous=\E[M, knp=\E[6~, kpp=\E[5~,
    kri=\E[1;2A, mc0=\E[i, mc4=\E[4i, mc5=\E[5i, meml=\El,
    memu=\Em, oc=\E]104\007, op=\E[39;49m, rc=\E8, rev=\E[7m,
    ri=\EM, rin=\E[%p1%dT, ritm=\E[23m, rmacs=\E(B,
    rmam=\E[?7l, rmcup=\E[?1049l\E[23;0;0t, rmir=\E[4l,
    rmkx=\E[?1l\E>, rmm=\E[?1034l, rmso=\E[27m, rmul=\E[24m,
    rs1=\Ec\E]104\007, rs2=\E[!p\E[?3;4l\E[4l\E>, sc=\E7,
    setab=\E[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e48;5;%p1%d%;m,
    setaf=\E[%?%p1%{8}%<%t3%p1%d%e%p1%{16}%<%t9%p1%{8}%-%d%e38;5;%p1%d%;m,
    sgr=%?%p9%t\E(0%e\E(B%;\E[0%?%p6%t;1%;%?%p5%t;2%;%?%p2%t;4%;%?%p1%p3%|%t;7%;%?%p4%t;5%;%?%p7%t;8%;m,
    sgr0=\E(B\E[m, sitm=\E[3m, smacs=\E(0, smam=\E[?7h,
    smcup=\E[?1049h\E[22;0;0t, smir=\E[4h, smkx=\E[?1h\E=,
    smm=\E[?1034h, smso=\E[7m, smul=\E[4m, tbc=\E[3g,
    u6=\E[%i%d;%dR, u7=\E[6n, u8=\E[?%[;0123456789]c,
    u9=\E[c, vpa=\E[%i%p1%dd,

Am I missing some configuration here? Is this how XTerm works? I don't really understand how's it capable of passing that test though.

EDIT: After Thomas Dickey's answer, I've indeed tried to redefine .Xresources to be without C preprocessor #defines. Here's the result:

!fonts&stuff
UXTerm*faceSize: 11
uxterm*eightBitInput: false
UXTerm*faceName: Fira Mono Regular

!Background & foreground
UXTerm*background: #fdf6e3
UXTerm*foreground: #657b83
UXTerm*fading: 40
UXTerm*fadeColor: #fdf6e3
UXTerm*cursorColor: #586e75
UXTerm*pointerColorBackground: #93a1a1
UXTerm*pointerColorForeground: #586e75

!UXTerm*borderColor: #343434

!Turning off scrollbar
UXTerm*scrollBar:  off

!Starting up with a geometry
UXTerm*vt100*geometry:   160x50

!Colors
!-------------------------
!black
UXTerm*color0: #073642
UXTerm*color8: #002b36

!red
UXTerm*color1: #dc322f
UXTerm*color9: #cb4b16

!green
UXTerm*color2: #859900
UXTerm*color10: #586e75

!yellow
UXTerm*color3: #b58900
UXTerm*color11: #657b83

!blue
UXTerm*color4: #268bd2
UXTerm*color12: #839496

!magenta
UXTerm*color5: #d33682
UXTerm*color13: #6c71c4

!cyan
UXTerm*color6: #2aa198
UXTerm*color14: #93a1a1

!white
UXTerm*color7: #eee8d5
UXTerm*color15: #fdf6e3

Loaded the settings without -merge just to be sure:

xrdb ~/.Xresources

And launched UXTerm:

EDIT2: Forgot to mention one (probably relevant) detail: if I get rid of the color scheme whatsoever, UXTerm starts to show colors at least resembling Alacritty's:

So the direction is kinda correct. But it's plain unusable to me in this state.

Answer 1

Alacritty ignores the resource settings, xterm uses them. Those S_xxx names are post-processed with the C preprocessor before xterm sees them.

Copying that .Xresources stuff into a file, and trying that shows a problem with the settings (some values are undefined):

> XAPPLRESDIR=/users/tom/app-defaults.orig uxterm
Warning: Color name "S_base3" is not defined
xterm: unable to allocate fg/bg colors
Warning: Color name "S_base1" is not defined
Warning: Color name "S_base00" is not defined

(I spent some time investigating palettes, e.g., solarized, a few months ago, finding that most of the webpages listing X resources have errors like this).

With the corrected palette: by default, xterm maps the first 8 ANSI colors into 8-15 if there's a bold attribute (that solarized palette doesn't have brighter colors there, of course). You can disable that by +pc (command-line option), or the corresponding resource boldColors:false

Answer 2

 PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

  setab=\E[%?%p1%{8}%<%t4%p1%d%e%p1%{16}%<%t10%p1%{8}%-%d%e48;5;%p1%d%;m,
  setaf=\E[%?%p1%{8}%<%t3%p1%d%e%p1%{16}%<%t9%p1%{8}%-%d%e38;5;%p1%d%;m,

Your prompt is not correct for your terminal type. It has hardcoded SGR control sequences for changing colour, and it has hardcoded the wrong ones, for another terminal type.

• Your terminal sets colours 8 to 15 in response to SGR 90–97 and SGR 100–107, which is what all the gibberish in the setaf and setab actually does. (The rest of the gibberish specifies that it sets colours 16 and upwards in response to SGR 38:5 and SGR 48:5, with the faulty separators.)
• Your prompt is trying to set colours 8 to 15 by setting colours 0–7 instead, and turning on boldface (with SGR 1). If you look carefully at your UXTerm screenshot you will see that that is exactly what UXTerm has in fact done, set a low-numbered colour and turned boldface on, just as your prompt asked.

The other programs are not hardwiring control sequences, which is why they work.

Don't hardwire the control sequences. Generate them with tput setaf and tput setab and use command substitution to place the result into your PS1 shell variable. Then it will work with many types of terminal and not just the one that you have hardwired.

Ironically, the hardwiring that you, or the person who did that in your prompt, have chosen applies to a small minority of terminal types. Only the linux-16color terminal type in the terminfo database tries to set colours 8 to 15 that way, in fact. To the majority of the world of terminals nowadays, boldface means actual boldface, a change in font weight, not colour. Do not use it as if it were a colour change.

Further reading

• https://github.com/microsoft/terminal/issues/5682#issuecomment-624583284
• https://unix.stackexchange.com/a/31697/5132 (the likelyhood of your having a missing terminfo on Pop-OS is slim anyway, even failing to take into account that other programs can use it and it is obviously there in your case)
• https://unix.stackexchange.com/a/204187/5132
• https://unix.stackexchange.com/a/71012/5132
• https://unix.stackexchange.com/a/347446/5132
• https://unix.stackexchange.com/a/16123/5132
• … and many more answers showing tput.
• https://unix.stackexchange.com/a/588898/5132