I usually use a sandy colour but it has to be full gloss to allow the decals to stick properly without silvering. If you don't have a full gloss paint just paint it with a flat paint then overcoat with a full gloss clear, make sure it is all perfectly dry before applying the decals. I use Mr Mark softer on the surface before applying the decals, once the decals are patted down I then hit them with a hair dryer for a few seconds, this makes the decals really hug the surface giving a painted on appearance.
Des.