Not a real solution for most applications, but mostly applies to the highly specific Projection Painting technique.
In this case the problem was mainly to do with the edges. My solution was to Alpha out the edges manually but leave their colour intact. That way the colors disappear as I wanted but they do not have the same level of aliasing.
In this case the problem was mainly to do with the edges. My solution was to Alpha out the edges manually but leave their colour intact. That way the colors disappear as I wanted but they do not have the same level of aliasing.