I thought Stadium of Rainbows was a good idea. It reminded me of Theatre of Dreams, so made mixed them together for the mighy Theatre of Rainbows which is currently being used by Colour City, Port Morrow, and also UNIV. CRAIOVA and Crewe Alexandra given their current state of vagrancy.
It also houses a unknown club but they live in the dressing rooms in the basement and nobody has seen them yet.
As for the nickname, it could be cool with the Norwegian translation. Fargenes by (city of colours) could work.