Best colour ey? Well that depends.
If the car is to be kept stock, Cosmic Grey looks amazing, it fits the OEM look of the car so well. Milano red for example looks terrible in stock form (imho) especially with the silver wheels.
NHB looks amazing when the paint is fresh and has been clayed/waxed and polished. But as others have said, a b*stard to keep clean. The Champ White really doesn't work on the EP3 imo, makes it look like those astra vans you could get at the time.
I've had nothing but light or dark grey cars so as much as a cosmic is the most desired model, I couldn't get yet another grey car lol.
However, assuming I've not had any grey cars in the past my list would be:
1. Cosmic
2. NHB
3. Milano
4. Silver
5. White