This took me about a week to build with world edit. You need to have the Automobility mod which I'll link here: https://www.curseforge.com/minecraft/mc-mods/automobility

The version is 1.19.2 and to get to the actual rainbow road, spawn in an end portal and go into the end, it's in there.

If you want to use it with the mod make sure you use larger wheels on your car to get up bumbs, either put them on manually or use an auto rickshaw.

If you want to use this map in a video or whatnot I don't mind, just make sure to give credit!