depends on what fish you are talking about. i think between the fish you have, and your list, you have too many fish. i think 6 or 7 small/medium fish would be all i would want to put in a 90.
you are not going to see a tremendous difference in color with multiple fish. it's not like they go dull being by themselves.
the flashing is caused by multiple things, courtship being one. you'll need a pair, one being the less colorful female.
if you are really interested in color, you should get a mated pair of flame wrasses, and remove the scooter.