There's a ton of different methods of multicolor printing each with different pros and cons - simplified
* nozzle that mixes from multiple inputs * multiple hotends on the carriage * swappable hotends * single hotend - retracts and switchs to a different filament, few methods here, this is what the AMS and pallete are **
You can do it with multiple heads, the problem is ooze. You'll need to either be able to retract the non-used printhead so that it doesnt ooze onto your print, or be able to swap it mid print. Either way here you'll still need a method to prime it. Some materials may break down in the heat of the hotend too while they sit there unused just baking.
There's some methods that make the blocks smaller, like using the infill as the priming section.