You can tint glass with Mod Podge and either acrylic paint or food coloring. Dilute your Mod Podge with water and add your coloring. Pour it in your jar and swirl it around so the sides are completely covered. Drain out excess and let dry upside down so it continues to drain. It takes about 24 hrs to dry. Be sure to move them occasionally so excess does not puddle at the opening of your jar.... Drying time can be quicker if you bake them in the oven at a low temperature