i was watching Neon Raven's stream last night and he'd changed the colour of his HUD to a cool pale grey/blue with red highlights. It looked damn fine and this is how you do it...
http://www.reddit.com/r/EliteDangerous/comments/2p3784/you_can_manually_customize_the_gui_colors/
As an example, this one is 'cool blue'...(sorry for image size...on iPad and can't resize it)...
You do need to restart the client each time you change it but hey, it's a hacky mod so is to be expected. Hopefully, ED will add this into the Options because it's only been requested since like day one! IMO, it could be hacky mod of the year.
EDIT: Some kind soul has already knocked together a previewing tool...
https://forums.frontier.co.uk/showthread.php?t=73760
And this is the original forum thread...
https://forums.frontier.co.uk/showthread.php?t=73419