The thick coat which is referred to as enamel has an indent around the markers (especially visible on diamond markers) - These very often have cracked dials and are a rare find in good condition. Where's the regular coloured dials are thinner and less prone to damage. The latter are much easier faked and so you'll need to know what you are looking at rather than taking a coloured dial on blind faith. looking for the correct deviations and spoils are the best way to verify a coloured dial
There is a way to verify for sure on a dial that is loose which I am afraid I shall need keep to myself for now: with the new found fake techniques there are certain points that need to be kept inside and away from the scallywags.
Sapphires however are a better quality item and I have not seen any abused examples YET.