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

Why would you want to do this?  Imagine that your RGB isn’t color, but UVW coordinates from a 3D render pass.  Now you can do texture transformations by using this tool to modify the mapping.  Also, if you have comps where you’re converting XYZ to RGB, you can use this to post-edit the tranformation, so you can apply spatial transformations in the form of XYZ -> RGB -> ColorMatrixTransform -> XYZ.

In the future I might add an input and output similar to the Color Matrix tool so you can insert a matrix found elsewhere, as well as generate an output matrix you can read off, but for the time being, input matrices can processed by the Color Matrix tool just prior to the ColorMatrixTranform tool, just remember to use 32bit float colors.

If you’re a bit confused as to what the tool is doing, try viewing the results in the 3D Histogram SubV.   Really helps you get your bearings.