Is it possible to set somewhere in configuration the color of the border between windows from red to black or remove the border completely?
To change the colour, you can set
xmonad.hs. They should be set to
#RRGGBB. For example, to set the focused window's border to black, set
focusedBorderColor = "#000000". The default color is
To disable the border, set
borderWidth = 0 in
xmonad.hs, or use
XMonad.Layout.NoBorders for specific layouts.