Hi,
I just tried out the gl-3.0 branch on Windows. I applied a bunch of changes mentioned in the "Big code cleanup" thread. I also had to add calls to glewInit() after glut's initialized, but I'm not familiar with glew so it could be that I installed it up incorrectly somehow.
Should "shift" be the remainder of the x position perhaps? I'm also not entirely sure how the vertex color should be correctly combined with the subpixel fragment colour. Multiplying at the end as is happening now seems incorrect, because multiplying by rgb(0,0,0) seems like it'd remove all subpixel colour.
scott