Well, it might be changing color. I find my acros rarely stay the color they were when I bought them.
Can you look closely and see if there is any flesh covering the skeleton? Are there any polyps visible? Sometimes you can see polyps out at night if they don't show them in the day.
It had blue tips when I bought it, and graadually turned brown. # of the branches are brown, the rest have what looks like coraline on it. I never saw polyps- but I'll look tonight. i think I've had it about a year.