I don't want to sound rude but after 6 montg of posting with bumps every 3-5 days without sale, there might be something wrong with either your price or product you want to sell(read color) or ad audience
I bet if you platidip those black you would sell them within weeks on kijiji
Purple only looks good on white or black cars so you arr limitting your client base. Black on the other hand would fit for red, blue, green...
Maybe you don't like matte black finish on wheels but you eon't be seeing them for long as they will sell faster.