To make the colored glue, we filled empty condiment bottles ($1 apiece from Wal-Mart) with white school glue and a squirt of tempera paint. You can use food coloring or liquid watercolor to tint, if you prefer. I stuck autumn and Halloween cookie cutters (a Wilton set - $4 at Michael's) to contact paper to hold them in place.
Meg simply filled the cutters up with the glue. I encouraged her to use different colors in the same cutter to highlight features, but she wanted to stick with one color per cutter. Just as well, because the glue did run quite a bit and the colors may have mixed too much. I've read that you can run a bead of hot glue around the inside and outside of the cutters to prevent the colored glue from escaping underneath, but, despite a lot of leakage, our cutters were still nice and thick, so I don't think it's necessary.
The shapes took a few days to dry, but they finally remained firm instead of sticking when we lifted a corner to peek underneath. The oranges and reds dried the slowest, probably because they had more pigment. After we popped them from the cutters (much easier when they're still a bit stretchy, by the way, than if you let them harden completely), we poked holes in the top and bottom of each shape and strung them together with thread to hang in the windows. For fun, I added some faces and other simple (very simple) features with a Sharpie before we hung them, like so:
|This was one that we left in the cutter until it hardened completely, and you can see that his hand and tail didn't pop out cleanly.|