Some bikes are manufactured with reflective rims. It seems to me we could have standardized reflective rims and reflective spokes. They don't involve colors, so no interference with individual preferences.
You'd have to convince the consumer and the manufacturer to give up rim brakes then- go fixed gear, coaster, or disc. Brake pads would degrade any reflective properties of the rim sooner or later, sooner if ridden in wet, grimy conditions- especially if someone isn't OCD about cleaning.