I finally have the proper ratio to make buttercream in my mixer and cover the paddles so it's nice and smooth. I make a triple batch but I need more than one color. I tried removing some and adding the color to the icing in the mixer and since the volume went down the beater wasn't covered and, of course, it got bubbles! So I've been reduced to coloring by hand. Is there an easier way besides making a triple batch of one color?

Not really. If the paddles are not covered, you are whipping air into the icing.