BUG: Cannot use bright colors

Cannot configure git to use brightred, neither on Windows nor on Ubuntu. 

Steps to reproduce: 

1. Create ~/.gitconfig with the two lines (or add to them to this file, if it exists):

[color.status]
        untracked = brightred

2. run `git status` from a directory with untracked files

Expected: output in brightred
Actual on Linux:
error: invalid color value: brightred fatal: bad config variable 'color.status.untracked' in file '/home/<username>/.gitconfig' at line 2 

Actual on windows:
 brightred=normal=white.