Could just be the lighting or the picture but most corals are not naturally brown. Browning can occur from lack of light or a number of water quality issues.
This could be the natural color but not likely, many corals i buy look somewhat like this but in a week or two under strong lighting and good parameter colors will start to emerge. Ive had frags go from brown to full flouresent colors.
If that is the case with this coral its not an issue as long as its getting proper water quality and light it will do well and gain more color.
Color loss can also be the result of excessive phosphate as well as slow growth. Looks like you may have a hair algae problem meaning you have a phosphate problem. If your testing near 0 for trates and phosphates then it is bound up in the algae, rocks and aand where is cannot be tested. Only nitrates and phosphates in the water column unbound are detectable with test kits.
29g Mixed Reef, 150w 14k Phoenix MH w/ Moonlights, Reef Octopus BH1000 HOB Skimmer, Ecotech Vortech MP10es, ReefKeeper Lite (Plus), PH Probe, Temp Probe, ATO, Carbon/GFO Reactor.