Is it possible to set the vertex color alpha component? I work in the game industry and often make shaders that rely on vertex color parameters for certain effects. This is often used to reduce shader complexity and material usage in order to improve performance. I normally paint the vertex color values in Blender, but there doesn't seem to be a way to paint the alpha component of the vertex color. Is there any way to set vertex color alpha?

Unrelated to the question, but it would also be awesome if there was a simple way to filter color channels in vertex paint mode like in Photoshop's channels box :)
There is no alpha component in vertex colors in Blender. The property is array with size 3, not 4.

You can have any amount of Vertex color layers though.