Is this in reference to a Form 3, or an earlier model?
On the Form 3, the printer prevents you from switching a tank to another resin outside the same “family”. e.g. You can switch between different Standard resins just fine (Black <–> Grey <–> White) or between engineering resins (Tough <–> Durable) but you can’t switch between the two groups (e.g. Tough <–X--> Black). It was discussed recently here: Tough 2000 resin
On the Form 2 and Form 1+ my understanding is you can switch freely. Of course you may not achieve as good results going from an Engineering one such as Rigid, to a Standard such a Clear. Rigid (and other Engineering / Flex resins) wears the tank faster and some remnants may get left behind. Also if switching from a dark resin to a lighter one (e.g. Black or Grey, to Clear or White), you might find the old residue “tints” the new stuff ever so slightly. The more of the original resin you get out, the better (just be careful not to scratch the flexible membrane / PDMS).