Hi,
This info is not (yet?) present in the latest documentation of grub. Here's what the legacy version has to say about it:
Code:
13.2.2 color
------------
-- Command: color normal [highlight]
Change the menu colors. The color NORMAL is used for most lines in
the menu, and the color HIGHLIGHT is used
to highlight the line where the cursor points. If you omit
HIGHLIGHT, then the inverted color of NORMAL is used for the
highlighted line. The format of a color is
`FOREGROUND/BACKGROUND'. FOREGROUND and BACKGROUND are symbolic
color names. A symbolic color name must be one of these:
* black
* blue
* green
* cyan
* red
* magenta
* brown
* light-gray
*These below can be specified only for the foreground.*
* dark-gray
* light-blue
* light-green
* light-cyan
* light-red
* light-magenta
* yellow
* white
But only the first eight names can be used for BACKGROUND. You can
prefix `blink-' to FOREGROUND if you want a blinking foreground
color.
This command can be used in the configuration file and on the
command line, so you may write something like this in your
configuration file:
# Set default colors.
color light-gray/blue black/light-gray
# Change the colors.
title OS-BS like
color magenta/blue black/magenta
Hope this helps.