I dont know how you are making your armour at the time so I cant really reccomend any colours.
If you are making all the details on the armour when you build it, you can use lighter colors because you don't have to worry about painting the details on which require shading to make them look as real as possible.
If you are just making your amour flat like the pepakura ones, I really suggest using a darker color, because it is a lot easier to shade and highlight in order to paint the details on.
Also, bright colors usually make imperfections stand out.
I always thought darker colors look better anyways. they look more ... professional. A white or silver MC would be awesome, but neon or light colors look cheesy.