OK decided to have another go at making RGB Layers using Justin's new color correction script. It's pretty clunky but much better result than the previous time I tried.
https://youtu.be/I5t89JzoE84
Here I'm using 3 layers of same video with a slight X and Y position shift on middle and bottom layers. Each layer has R, G, or B isolated. The R and B layers have what I've saved as 'lighten/screen overlay'. Without the position shift the video looks normal.
Code:
img1=0;
img2=input_track(0);
gfx_blit(img2);
gfx_mode = 1;
gfx_blit(img1,0);
And then above that I have a tracking error stock with green keyed out.