Any recommended tutorials for learning to design for multicolor?  

RE: Any recommended tutorials for learning to design for multicolor?

Modifying existing single STLs can be hard. There are a couple of good videos about using MeshMixer for such work. One is from the people that make the Palette and it is coloring a parrot and another is coloring a model of an animated character. In my experience, however, if you are trying to work with a model that has a lot of detail it all starts to fall down as the splitting ends up generating weird artifacts that then prevent further splits or just make it unprintable.

Building a model from scratch, however, is simple (in relative terms). You build your model up as you normally would, but you do not join the parts that will be different colors and export them as separate STLs. PrusaSlicer will then put them back together for you as one model with parts you can associate to different tools.

As a simple example let's say you wanted to create a 100mm tall cylinder with a color change every 20mm. For the single color version you would create 5 20mm talk cylinders, stack them on top of each other, and then merge/union them (well, you'd really just create one 100mm cylinder, but give me a sec ;)). To make it MMU compatible, you simply leave off the step of merging the 5 cylinders. Their relative positions will be stored in the STL which is how PS knows how to reassemble them for you. Clearly a more complicated model will be more complicated, but that's the gist of it.

For example I have a test object that is a 20x20x20mm cube made up of 4x4x20mm block where I stagger the colors on each row (e.g. first row starts with tool 1 and ends with 5, second starts with 2 and ends with 1, etc..). Rather than have to designate each 4x4x20 part in PS I merged the parts in my design so the result is 5 parts rather than 25.