The definition of
font-lock-comment-face includes many variants for cases of varying color support.
chocolate1 variant is used when there are at least 88 colors available and the “background” is “dark”.
Firebrick variant is used when there are at least 88 colors available and the “background” is “light”.
The difference is caused by some code that gives special meaning to TERM values that start with
eterm: it considers them to have a “light” background.
You should be able to customize
frame-background-mode* to its
light value to always use the “light” color variants.
If your Emacs is not new enough to have its own
term/screen.el, then you will also need to adapt one for yourself that makes the appropriate color-adjusting calls. You might use the one from Emacs trunk, or I have a Gist that includes a
.emacs.d/lisp/term/screen.el (with some extra bits to recognize the modifier+arrows/Home/End sequences provided by tmux’s
xterm-keys option), and the
.emacs modification needed to let it automatically load.
Of course, there could still be other bits of code that directly check the TERM value and do something different for
* M-x customize-variable frame-background-mode