Here's what I mean in pictures. My mesh already has vertex color info ("colorSet(RGBA)"):
![Image](http://i68.tinypic.com/r76hwm.png)
So I activate the "Keep Vertex Colors" option (because I want color information to be preserved):
![Image](http://i63.tinypic.com/29dh7xe.png)
But As soon as I start moving the slider then the additional (black/empty) vertex color set gets created and added to the mesh. So the result is the new (black/empty) set becomes the active one and negates the existing one:
![Image](http://i65.tinypic.com/34sjgnc.png)
Could you please take a look at this issue? Thanks!