Phishybussiness.com has great BTAs
And Liveaquaria.com in the divers den has WYSISWG btas from time to tme.
((I haven't ordered any from them, I ordered my RBTA from reefermadness.us and it was great and still living. btw all three are sponsors here. There are many claims to getting healthy anemones from all three vendors. And I haven't mentioned all of the good vendors as well))
Yes, avoid transparent flourescent colored BTAs, and white ones as well, they are usually bleached which means they have lost their Zooxanthellae. Also try to avoid purchasing one with a gaping mouth, you want their mouth to be tightly closed.
Ordering them online and buying them at a LFS can both be risky. They can be super stressed from the shipping and can look like crud, but BTAs are fairly good at recovering from them if you acclimate them well ((I drip acclimate for several hours)). And at a LFS they can be kept in inadequate conditions which make them unhealthy as well.
So as long as you know what to look for in purchasing a healthy one, and how to care for one, they can be fairly hardy as anemones go.