Yes you can do a variety of colors together, they don't care, they are all the same species (assuming they are not the wild caught altums - spelling?). Best to add all at once so they all have an equal chance at the territory. If you stagger it, the existing angel(s) will have possession of the territory and may be more aggressive.
How big is your tank? I have a spawning pair in a 60 gallon with other fish and I would not do more angels. I suppose if it was only angels in this tank I could do more but I have other inhabitants. I also have one in a 29 gallon tall tank with other inhabitants.