I think it may be possible in poser to get transmitted light of various colours, along with refraction.  it just didn't work when I used glass pieces of finite thickness in poser - FFRender didn't transmit the colour of the glass onto another posersurface.  supposedly this is because that would be an example of caustics, as mentioned by athan above.  I'm assuming the above example in carrara (glass pieces with zero thickness) is the desired effect.  the transmitted colours appear on surfaces in carrara, whether or not caustics are enabled.  I can see it in trekkie's first example above, but it appears to be a blurred gel or mask on a light, as mentioned.