Just a heads-up. I have experienced colour bleed when using white PLA filament and auto-refill from one spool to the next on the Snapmaker U1. The printhead that contained the new white spool had previously been using red PLA. The result was a thin red layer on the white part being printed. I will have to remember to do do an additional filament load of the printhead for the new white spool before starting a print.
That is always a possibility. Remnants of old filament can hang around for an awfully long time, and be more noticeable if it is a strong colour when the new filament is pale.
I’d actually expect that to be a thing. It may not be purging enough, realistically.
Another option is to run 100mm of this through before changes