pothos will turn color like that if they are not watered enough...since you just put it in a larger container, it's possible that it wasn't watered throroughly enough to compensate for the larger size of the pot.
they will also turn color when overwatered...lol.
so, you're going to have to check the soil and see which it is!!
also, this is a major shock (3 years is VERY long to wait to repot) for the plant
...so, some leaf loss is inevitable.
if you put it in a different location, too, that will also cause problems - they don't seem to like quick changes too much.
can you post a pic? that would be really helpful!