Dealers get stock on consignment, for a limited period, then they have to pay for them. They need to sell them before the consignment ends, so they only pay as they receive the customer's money. For this reason, they will only stock colours they know will sell. They will resist risk. The customer can order their choice of colour, and wait, ..... and wait, or have one from stock, which will be grey. This is why cars are predominantly grey, and why vans used to be always white. Years ago, when I was controlling stock at a large Rover dealer, you should have seen the panic on the sales manager's face when some colours arrived. I took a few risks, all got sold easily, but usually with a warning not to do it again.