You could...the color will probably fade fast...like the hummingbird feeder's do ...also could use bottle for oil lamp w/special wick & topper. Jeanne S.

Instead of water, you could try colored dish washing soap. It comes in a huge variety of colors these days and it looks really pretty with the sun shining through it.

How about filling them with marbles? Or tumbled colored glass? Small sea shells?

Or pouring paint inside & twirling around ...diff colors.

in the sun the food coloring will fade within a couple of weeks here in the south. You can just add more though.
Tally HO!

I've made some awesome Christmas ornaments - using clear bulbs and pouring in acrylic paint and swirling it around.
I've often wondered if it would work outside . Here's how it's done :

Here is a link that might be useful: Swirled paint ornaments

I've also used nail polish.

MY CROW from a 1 gallon clear wine bottle.

{{gwi:142909}}

r_murray, LOVE your crow!!!

I thought about maybe painting our last name and farm, with a letter on each bottle and attaching those to the top of a fence or something.