If I delete a Showroom paint, will drivers who’ve raced the paint still be racing the paint?

Yes. If you remove a Showroom paint, the users who have already selected to use that paint will continue to have that paint assigned until they change their paint.

Trading Paints cannot accommodate requests to remove paints from users who raced with a paint you deleted from the Showroom. Be sure you only upload finished, original work you don’t mind sharing.