Since your question is posted in the ships section, I assume you're referring to ship colors, so here's a basic list of what you'll be needing...All of the colors listed below are available from White Ensign Models in enamels, and Testor's Acryl in acrylics.
For USN WW2:
5-N Navy Blue
5-O Ocean Gray
5-H Haze Gray
5-L Light Gray
20-B Deck Blue
Anti-Fouling red (Oxide Red)
Flat Black
These colors will allow you to do Measure 21, 22, 31, 32 colors schemes for WW2 USN ships.
For modern USN:
#27 Haze Gray (FS 36270)
#4 Deck Gray (FS#36008)
For IJN WW2
Sasebo Gray
Kure Gray
Maizuru Gray
Yokosuka Gray
Type 1 Camouflage Green for carriers
Type 2 Camouflage Green for Carriers
Deck Tan FS# 30318 is slightly darker.
Lino Brown
If you want WW2 Royal Navy colors, they're far more complicated than the USN or IJN (except for their modern colors)...
Hope this helps.
Jeff Herne