Recycle glass bottles - Mix water, glue, and food coloring, coat the inside of the glass jar, then turn it upside down to dry for 1 hr. After that, leave it out to dry for 2 days (instead of baking it)
How to: Dye Clear Glass ANY Color (A New Technique)
Remember the Mod Podge + food coloring technique for painting clear glass? That was cool and all, but I spotted another method using Vitrail glass paint and acetone (nail polish remover) that allows the bottles and jars to be used as actual vases, as the finish is waterproof! This treatment provides for more depth of color as well.