This issue was reported to SCP Mantis
Issue 2059 along with a proposed patch to better handle undefined cases in the future.
MediaVP corrections are being worked on and will depend on whether or not the proposal for expanded Briefing Text Colors catches on.
Speaking of, here is what I have so far, comments on additional colors would be great: (white ($w) is default text color, $b, $g, $r are default colors available already)
Bright White: $W
Standard (default) White: $w
Black: $k (Black)
Standard Blue: $b
Bright Blue: $B
Standard Green: $g
Bright Green: $G
Standard Yellow: $y
Bright Yellow: $Y
Gray: $e
Silver: $E
Violet Gray: $v
Violet: $V
Standard Red: $r
Bright Red: $R
Pink: $p
Bright Pink: $P
Additive (non pre-existent colors) are: Silver, Violet, Pink and Bright Pink. The other colors were already defined in alphacolors.cpp, with the exception of Yellow/Bright Yellow which got redefined as they looked more like Lime Green. And I realize that on a black background Grey looks really dark. In game, it's very legible and distinctive from the standard text.