Hello xADrX,
Unfortunately, I will be
Rejecting your map.
The theme isn't original, as there are many rainbow themed maps already. Please check the document linked in this thread -
https://manacube.com/threads/parkour-list-with-theme.20194/ to make sure your map idea is original.
There isn't really a main build for your map, in the future, try to have a main build that represents your map theme, then incorporate your parkour into that, rather than just having jumps floating over the void.
The parkour is very repetitive, as you only used normal blocks. Try to experiment with a larger variety of blocks and items when building jumps, as well as the ways you utilise them, as this will make your map more enjoyable to complete.
The length is a bit long for a medium, and the difficulty is good for an easy map.
Thanks for submitting your map! I hope to see more maps from you in the future.