Another variation of Montipora digitata, a thin branching SPS that tends to grow pretty fast under the right conditions.The polyps are a bluey purple. Under some lights it can look either, although please note this is the blue, and there is actually a violet digitata out there also.
Digi likes lower light than most other Montipora. The branches tend to grow extra thin and spindly when they are growing in lower flow. Conversely you’ll get thicker, stronger growth in strong flow.