Fusion 6 added a Color Matrix tool that lets you enter your own matrix by hand, but the biggest problem with it is the lack of any methods to modify it with. You can’t even assign controllers to it.
Fuses, however, let you use handy methods to modify a matrix. I’ve used some of them to create an RGB equivalent of the 3D Transform tool. It has a similar UI, just as 3TT does, but this modifies RGB, not XYZ or UVW.
Color Matrix Transform fuse
