Hello,
First of all, the build itself does look nice, but the theme is very overused, as there are many rainbow themed maps (Colors, 3Rainbows, Rainbow road, carpetrun to name a few). The parkour is an okay length for the difficulty, maybe a little bit too long, but that isn't really an issue. The parkour itself is a good difficulty for an easy map, however there isn't much variety in the jumps, as many are single block jumps, and it does get quite repetitive, so I would recommend you experiment a bit more with the style of jumps you use when building maps.
Good luck! :)