Like Scottayy, I purchased a bleached bubble tip anemone. For months, I couldn't figure out why it looked like it was shrinking.
There are degrees of bleaching. The most severe is total bleaching, in which the anemone has lost ALL of it's zooanthellae. In that case, it needs a new source, which will typically need to come from a member of it's own species.
So, I purchased a second BTA, and within weeks, the original began to darken up. It is now a nice greenish brown color, as it should be. Sadly, the second one I bought had an injury to it's foot that I didn;t notice right away, and it died.
Saving a bleached anemone is slow, difficult, and will not always work. Good lighting, target feeding, and proper water quality are the biggest concerns. If it is totally bleached, as yours appears to be, it might need a new source of zooanthellae. If lighting and feeding do not bring about an improvement, consider placing it with another one for a couple of weeks.