Damsels and clownfish are related.. cousins if you will. There are many species of damsels that will take residence in anemones much like clownfish will. They should be ok with each other, but like any species of mixed clownfish keep a watchful eye out, as problems are not uncommon.
As for the color, True percs have a notably darker area between their white strips some are less than others, in some fish the black can completly consume the orange body except for the fins. There is no indication how much or how soon this will happen for you. Only time, patients, diet and maturity will dictate what your end result will be. The shades of orange and black can be affected more by diet and stress, as the amount of black will change with maturity. Good Luck and post pic if you can.