Sponge Watermelon Squishy Tutorial First, cut a watermelon shape out of the sponge. The color scheme is as shown in the picture. Gradually blend colors on the sponge watermelon. The tip of the watermelon should be darker in color. Add a bit more red to the paint, then blend the watermelon tip again. Paint the bottom with a slightly yellowish green. As shown in the picture. Finally, add a cute expression, and the squishy is done!