The Basin will not accept more than one Magenta Paintball since they do not stack, making it impossible to add the 4 paintballs required for the recipe to work.

Confirmed - JEI lists this as a way of making Chromatic Compound but in fact you can't insert enough magenta balls into the basin for it to work. The mechanical crafters is the only way that works.

Mechanical crafters are the intended way to craft Chromatic Compound, looks like JEI showing a compacting recipe was a bug that was fixed in Create 0.3.2g.