
This is why one just can swap bulbs for sets, you can't go mixing or changing the bulb voltages. If you are curious as to what your light sets have check any documentation or labels that come with the sets. If you have any sort of paper work in the box or poly bag then it should have some indication of bulb voltages.
Back to colored sets, none of our distributors have 20 count minis that come in anything beside clear and multi. Sure there may be someone out there that has them, but the big names in the game that we go through sadly do not. There is one "work around" but it takes extra sets and some patience, our multi colored have Red, Green, Blue, Yellow, and Pink. Normally our 20 count multi sets have 4 bulbs of the 5 colors on one string, so you can take 5 sets you can mix and match the bulbs to make 5 sets of complete colored sets. And before the wheels start turning, no we don't do this. It's about as simple as stacking Lego bricks, so you shouldn't worry.
Another question that we get asked is if you can clip the wires on a set to shorten it. No, it'll screw with the voltage of the set itself, and it's better to work around it than kill the string and have to buy another!
--
Zach