Editing Single Color Holiday Lights to be Multi-Colored

I think the problem may have to do with snow. I placed a bunch on a lot without snow and they worked just fine, but on that lot I was testing with snow it did what I showed in the picture. Although it was a bit inconsistent and glitchy about it. Like I could place the tree indoors on the snow lot and then move it outside and it would look like it's supposed to. But then if I placed another one next to it, that one would be messed up, and it would bleed into the aforementioned one that wasn't.