How can I keep colors on chocolate lollipops from bleeding into each other?

let them dry longer before adding the next colour. make sure the second colour isnt too hot and melting the first colour again.
xx

Thanks brinces_b! Do you recommend using the refrigerator or the freezer for setting the chocolate?

No. Chocolate sets over pretty quick naturally. Te bigger the piece the longer it needs to sit.
the fridge and freezer are extremes of temperature, as well as usually having more moisture in the air, neither of which chocolate like. So while it may help it to set, u may end up with more problems.
xx

Brincess is right. I also found that by setting the chocolate in the fridge or freezer, the colors separate from each other when you unmold the pops.