The Polyps of this Rainbow Monti are bright green within the corals center section. On the leading growth edge polyps turn orange/red. What makes this coloration change even more interesting is that polyps located in the area between the leading edge and center section have pigments with a spread coloration located spectrally between red and green. As you travel outward from the center section the pigments change from green to yellow to orange and then finally reddish orange. Thus the name Rainbow Monti. The faster the coral is growing and encrusting the wider the reddish orange region. In brighter lights there can also be more reddish orange polyps. The main coral coloration is blue and the surface of the coral has many small bumps or tuberculae. (reeffarmers)
I have had this monti for over 5 years now. While many reefers can grow it, the conditions must be just right to get the full polyp color variation seen here. My tank had the perfect monti growing conditions for about 3 years when this photo was taken. Alkalinity plays a big part on the coloration.