My experience in manually changing filament on my old printer. : There was often tiny gaps between color layers that ultimately made the model weak. Sometimes blobs instead.

(I would pause and change filament at a specific layer to get a multicolor print without a multicolor printer).

To solve this I would add a cylinder object to the plate so that the first place the head went after a color change was to the cylinder to get the filament back up to the right flow rate.

The pressure changes from changing filament is why the printer usually does a quick line at the start of a print. And why it’s necessary for multicolor changes.