Wait for the return to come back.
In the refund buyer window, before issuing the refund, report buyer for returns abuse - explain its a change of mind return buyer wanted colour not available in that listing and quantity not ordered.
Refund the buyer
Add the buyer to the blocked buyer list.
If you've left feedback automatically consider if you want to leave a follow up feedback, within the rules, as a breadcrumb trail for other sellers. Buyer ordered one dice and would have liked more so returned for refund or similar.