Two Spot Bristletooth Tang?
 

You may be able to get another tang in there (yellow or regal), but because of the size of the tank, it may cause aggression between then when they start to get bigger. Nice fish though.

Thank You, wont risk it....:)

I have one of the above fish:
2 Ocellaris Clownfish
4 Pajama cardinals
3 Yellow tail damsels
2 Emerald crabs
2 Scarlet Reef Hermit Crabs
1 Sand sifting star
1 Haitian Reef Anemone

I would like to add another colorful fish, what would you recommend that is reef safe?

You can go with an dwarf angel fish Dwarf Angelfish: Flame Angelfish and other Dwarf Angels.

I've been told to avoid any kind of angle if I plan on doing any kind of soft corals or clams and my wife wants a clam in the near future....

O. We'll it's a hit and miss. the reef i'm tending at work has 2 angels and they are doing well and not nipping any LPS or softcorals, but again it's a roll of the dice.

Your tang is a Ctenochaetus genus, same as the Kohl Tang, Chevron Tang, and Tomini Tang. I have a Tomini in my 180, and have kept the Kohl at home in a 55 gallon. Generally, Tang of the same Genus display similar behavior and will not be as aggressive towards other Genus.

This rule of thumb applies very well for larger aquariums, but in a 90 gallon i'm not so sure i'd chance it. The Ctenochaetus are the most passive of all Tangs, and would probably be bullied by any members of the Zebrasoma genus in any aquarium less than 6' in length. This includes the Yellow Tang.

For the record, any of the Acanthurus tangs, including the Paracanthurs Hippo Tang, are out of the question for a tank of your size. They grow way to large to consider in this tank.

I also would not personally add any members of the Centropyge angelfish genus, which are the dwarf angels. I have witnessed many Tang become offended to these fish, as they compete in nature for a common food source, namely algae.

Here is a great link for anyone interested in the possible Genus combination's of Tangs:
Surgeonfish, Tangs, Unicornfish and Moorish Idols

Thank You....