I know your pain, I'm allowed 6 but due to the size of my breed vs Chicken House, stick to 4. I used to raise hatches until 6-8wks old chicks for a friend so got to "test" out several breeds ... Seramas, OEGB, Australorps, Orpingtons, Wyandottes, Easter Eggers, Silkies, RIR
Orpingtons are my favorite, they are easy & friendly. Have tried keeping a mix "flock" but have learned all of one breed or at least two of a kind works best, no odd man out and never an odd number flock.
Keeping an odd number flock, two get cliquish although they get along
Same as when you have 3 of a breed & 1 differ
Keeping a pair of 2 breeds, seemed balanced
What works best for me is 4 of a kind, so maybe if you chose a breed that has different coloring, that may keep it colorful.
Have not tried 1 of 4 different breeds .... yet