I heard from @AGulev that someone were wondering how to create a custom GUI material that could turn specific nodes greyscale, so here is a super simple example how I would do it.
I’m hijacking the z-component of the position, since it isn’t usually used for GUI nodes. If the GUI node has a z value of 1 the node will be 100% greyscale and likewise if it’s 0 it will 0% greyscale (ie full color).
This also means that the amount of greyscale can be animated, my animating the z-component with
gui.animate. You can also set the z component for a parent node and will automatically affect any child nodes as well, as seen in the example video (the 5 nodes to the far right are childed to the white box at the bottom).