Invert to alpha
When working with vector- created art and the source art is unavailable, modifying the art to create a logo can be a pain, to say the least particularly when it’s flattened and the background needs to be knocked out. A careful combination of Invert (Command-I [PC: Ctrl-I]), Color Bal-ance (Command-B [PC: Ctrl-B]), and layer Blending Options (Control-click [PC: Right-click] the layer name) can yield simple background knockouts of one- or two-color logos without making a mess.