Thanks for the reply GTs58.
Im not too sure if this would be a base to another color. The reason being is that if it was a base then it would be a base to sky blue paint. The problem with that is the lettering on my chainguard is blue. Which wouldnt make sense to have blue lettering over a blue paint job. The lettering seems to be screened on, its definitely not a decal.
My thoughts were that it was originally painted grey and screened with blue lettering. The problem with that theory is that i cant find a photo of another fastback with that color combo on the chain guard.