Check price variance between black & grey. Just a guess however I'll wager grey interior color outsold black. Very possible you can get grey color raw material for similar price and it may match "good enough" for some customers with grey interior. Painting would still be an option. Also, check out "hydro graphics" as an economical method for providing customers not only "color match" but also custom prints. Virtually anything is available. PS: Injection mold initial cost is ouchy!