Pop...
Are you using the earlier revised HUD that myself and Doum worked on alot? The current, and better, new HUD from Neutrino doesnt have the color button that Im aware of, and its "cage" function works instead of the color button. Regardless, I have tried to repaint the older HUD to a "useable" RED and got tired of going thru MSPAINT to get it working, so I quit. Sorry for the bad news, but thats how you have to do it. Repaint all the .bmp files in the HUD_VC folder to a color you want. They should be named something like "HUD_Caret_0000FFFF.bmp", where the 0000FFFF or whatever it is, is the hex code to differentiate between colors. Just use MSPAINT to repaint all the files with the 0000FFFF ending to a red that you like. But keep in mind its a painfully long process and be sure to back up your original FA18_HUD_VC folder before starting.
If I confused you sorry, just PM me if you have questions or for additional details.
Later
Sludge