We saw both a red and a black lionfish in the Phillipines, both at Balicasag, which is an island that has a government operated dive resort. We stayed there because you can snorkel offshore. There were a surprising number of villages nearby, and there is only a small area that is marine sanctuary, but it is a larger area than we found elsewhere. The snorkeling was beautiful, with shallow areas as well as a lovely, deep wall that goes basically all around the island. Snorkeling here was excellent - despite the large number of daytrippers and boats, we always had space to ourselves.
The first snorkel, a vibrant red lionfish: