This is fairly simple but deserves it’s own explanation. You can certainly buy colored water at many stores, but you should know that this typically isn’t some sort of professionally done colored water and is more often than not just water with food coloring added to it. You can save yourself a lot of money in the long run by simply mixing your own colored water. If you’re going to make your own colored water for your clear glass vases you’ll want to mix about a half a cup of baking soda with a full cup of vinegar into your water. Mix these together very well and then add glycerin and corn starch to the mixture. Once you’ve mixed this let it sit for about five minutes then add the food coloring of your choice.
If you just food coloring to the water then it will settle at the bottom of the clear glass vases eventually and not look correct. Adding the other ingredients helps to add a thicker texture and make it look as though the water is actually the color you selected instead of it looking like the water has something in it. Play around with your colors and see what turns out best for you. If you can find a place that specializes in colored water made for clear glass vases and offer a good price then you may wish to stick with that as it takes away from some of the mess but is considerably more expensive.