Hi Christian! I am Spanish native speaker, is like saying the color are pretty but in a poetic way, you just do this type of phrases for writing. I actually teach Spanish with both: grammar approach but also I really like to explore poetic and different rhetoric tecniques, spanish have lotsss of them and they are quite beautiful :) Hope this answered your question! :)

Yes, it is strange, i suppose it is written like that for the metrics of the song, but is not the nlr al Way You would say it.

Still, it does make sense and native speaker Will surely understand what it means (i'm native speaker)

Poetic license, same as here:

In Xanadu did Kubla Khan a stately pleasure dome decree = Kubla Khan decreed a stately pleasure dome in Xanadu