The citadel is sort of an upside down cone with several cities on top, in the center there's a massive tower where the council lives
Around the citadel there are many MANY large rings that float around it, these are sort of like luxury housing. Collector owns a small one that floats around the bottom, not many people even know it exists
And further out than the rings there are space stations that examine incoming spacecraft and will intercept anything that seems to be a threat
For colors imagine the citadel of ricks from Rick and Morty, there's a lot of gold. (As you could probably guess this was greatly inspired by it)