The Caustics Generator website is currently down. Here's the link anyway for when they fix it. I can't find a copy of the install file yet but can post it when I find it if you want. 

http://www.lysator.liu.se/~kand/caustics/

The Gel works better with infinite light and a low brightness. Make your gel as big as caustics generator will go with as many foulds in the light pattern as possible, otherwise the pattern is too big.  I used a round light up high and changed the gell mapping to cubic to make the pattern size even smaller.

You have the option to create a blue pattern or black and white. Black and white works best for me because the blue pattern stains the light as it goes through. If you use black and white you can change the color of the light to yellow green or blue and see how it affects your scene.