This is called fading and can happen for different reasons. One reason is too much light can fade the color. Another reason has to do with the symbiocticZooxanthellae a brown-yellow algae that lives in coralโs gastrodermis. Sometimes , especially when the coral moves from one light source to another IE Metal Halide to LED or visa versa the coral will eject the current Zooxanthellae so it can host another more suited to the new light. This will cause a temporasry fading and is of no real significance. However one must determin if the lighting is generally too strong for the coral. Also one should determin if it is RTN rapid tissue nacrosis and this is done primarily with SPS. Looks like you have an LPS there and I would say if it is well extended as it seems then it will acclimate and do fine. Color lose it a common unwanted occurance.