i remember years ago a thing about different colour escort cossies, problem is it changes every year
there was a thread on the RSOC last year aswell.

white, red, mallard green, imperial blue & auralis blue were quite common colours, ash black were mainly small turbos, not loads of petrol blue ones but the rarer colours were gloss black, jewel violet, polaris grey & silver, i was told there were 100 gloss black, 50 polaris grey, 50 jewel violet (inc montes) & about 16 silver.
you can never be sure though, i had a guy give me a list of reg's for silver cars before, 3 of them were off my car, old private plates etc..