Red tail catfish question?

i have 1350 gallon aquarium with a 27" red tail catfish and a 23" silver arowana that i bought when they were both around 1 foot, and i just bought a red tail catfish baby about 2" in a 75 gallon grow out tank for now and its tail and dorsal fin aren't red, is there something wrong or does it just take a couple weeks or what?