Board Thread:News and Announcements/@comment-26036275-20150325211140/@comment-24577221-20151011150422

There isn't a "black" Glowbe, exactly. There are Glowbes that have very little colour, so they look very dark grey. The closer you get to ⅓ each of red, yellow, and blue, the less colour there is. It's a matter of combining mixed-colour Glowbes to get closer and closer to those fractions.