For what it's worth I'm running Windows 7 Professional 64-bit SP1 and TortoiseHG version 2.8.
The yellow scheme for the status.unknown items works well on a black background of the command line but not on the white background of the GUI.
I added red_background to the status.unknown line in the [color] section of Mercurial.ini. It changed the output of the hg status command as expected.
I went back to the GUI version and there was no change. I thought it must need to be reloaded so I went to Global settings for the GUI, made a change to an option, saved it then changed it back. I thought it would cause a reload of the options. No change.
It did say to restart all TortoiseHG programs but I had nothing else open.
Barring a lengthy restart of the machine what should I do?
Update #1
It seems that the GUI ignores the background values in the [color] section. I changed the color to blue (unreadable in the command prompt), rebooted and the text became blue in the GUI, but the background stayed white.
TortoiseHG reads Mercurial.ini on the fly. After I rebooted the computer I could change the colors without doing anything other than updating the ini file.