I would say most of the time for me at least, 70% of acropora will loose color for a month or so. Paling, browning or greening is common place. After the coral gets happy again color will come back and in many cases will have a slight color shift or in rare cases a major color shift, these changes in color are not always for the better. Yeah I had problems with browned acros for a while. Just what I have experienced with adding new sps frags. Its worth mentioning what that little frags goes through before it ends up in your tank. Fragging, glued, grown out hopefully, shipped and sometimes not under the best conditions, dipped for pests, maybe QT for a few weeks, put into a different tank with totally different water, different lighting and that goes double if QT was done first as does the different water. Its no wonder corals will brown or bleach and just loose color in general, its amazing they survive at all.