Most of the press manufacturers seem to stick with the following colors.
Red - Lee
Orange - Lyman
Blue - Dillon
Green - RCBS
Black - most of the vintage stuff; Hollywood, Texan, etc.
Gold - Spolar
I'm thinking of sprucing up one of my Hollywood Universals with either lime green or purple. It would definitely add some pizzaz to an otherwise dull press. How much would it increase in value?