This is the link to the motability Q&A web page about paint choice, it basically says you need to ask the dealer as you might get solid or metalic paint free, but you might have to pay for premium paint options. So it appears there are no set in stone rules, and it’s at the dealers discretion.
https://www.motability.co.uk/get-support/faqs/which-colours-are-there/
Daughters motability car Hyundai Tucson Ultimate self charging hybrid Serenity White Moss Grey interior.
My car SEAT Ibiza SE Tec 1.2 petrol TSI 2017.