Fill these bulbs with purge waste, skirts, brims, supports, or any other little bits of otherwise wasted material to add some color to whatever form of string lights you've got laying around, fairy lights, christmas lights, you name it.

Two bulb types, one simple and one with some twist to it. Both measure about 2in tall by 1in max OD. Fill bulb with material, slide the wires of the light through the slot in the cap (one of the pics shows this), then insert into the bulb which should be a snug enough fit to hold itself, but still easy enough to remove with a tiny bit of force. Printing the bulbs in vase mode yields a great result, but the seam really shouldn't be a big deal so feel free to print a plateful with one wall and no infill.

The amount of material will probably vary based on light source/# of lights per bulb, regardless I'd recommend lighter colors. In my pics I used fairy lights with some bulbs having one light and some two with varying amounts, colors, and sources of fill.