We put up a great free model by Remco and got some feedback about the way he made the lens material. The lens has beautiful coloration and the way Remco achieved that was by using the Thin Film Shader which is new in R18. The effect can be used for lenses, bubbles, water, and anything transparent that has a little oily, colored gloss to it. Hope this tutorial helps, it is super easy to set up.

You can get the model Remco made here