Lots of misinformation about the CXI emps! (CXI=christmas island)
Not ALL CXI emps will have the orange tail. I have had plenty that didn't, and plenty that have.
The juveniles you cannot tell if it will be orange or yellow. Most likely yellow, as most people agree the orange tail has to do with diet in the wild (what diet, they still dont know)
The smallest adult i have seen with orange tail was just under 4". for this ONE adult at this size with orange tail i've seen 10x more with yellow tails.
Your best bet is to find a small adult changing or just changed with the orange tail, and HOPE it keeps it. A lot of the adults with orange tails will lose the orange color, and revert to a yellowish color - still nicer than just yellow, but not as orange as most would like.
I have even seen some with nearly red tails - which was incredible. However, very very rare with this deep orange/reddish color.
I love the juvies. they are bullet proof, and are much deeper in color than normal emperors. the only choice for me if i was going to keep one.