This model was set up for it already in the .3mf file. It stops, moves the toolhead over, automatically unloads the filament, and waits for me to yank it the rest of the way out then stick in another color. It then purges the nozzle a bit to get the main color fully flowing and asks you if it’s correct before proceeding. I did this like 7 times for this stupid half-failed box lol.

Edit: Also, you can left-click the plus sign on the layer slider at any height you want after slicing in PrusaSlicer to add manual color changes in.