Coloring of it depends on it's health, light, and nutrients in water. This stuff killed almost everything in one of my tanks years ago. Before I believed in testing water parameters. Pulls ph and hardness down very fast. Thrives in tanks with low oxygen and will pull oxygen low. Don't make sense but will suffocate fish but yet lots of air stone will almost kill it out. If it gets out of control use some hydrogen peroxide in one of those injectors. Max 1 mill per gallon better to be on the less side. Just slowly inject it into the mats of it. Will turn red them pale and then gone.