im not shore if this tequnique has been doon before but here goes.
its been extaurated because its a test.
I like it, don’t know if it’s been tried before. Did you do anything tricky or is it just light through colored glass material?
Use different colours!! Forking WINDOWS!
Interesting technique… I did something somehow similar to this picture, but I think yours is more interesting lol. 
I wish that Blender could do more of complex colors coming out of a stained glass.
sorry about the colours.
I am working on a complicated stained glass window i think its possible (it is with my technique anyway).
its a lot more complicated than a spot light through a coloured material.
If you came up with a new technique, then I’d be very interested in knowing how you did it. perhaps a tutorial? hint hint.
a tutorial might be on the way but first im gonna try do a full blown pic witch is taking some time
add a nice coloured texture to the light…
put a glas window with the same texture as the light in a different layer
say to the light with the glass window to ignore that layer
fiddle with the settings
thats it… i guess
Someone else did somthing like that on a V. Complex window…I Believe they used a Env. Map for the light texture…I forget where I saw that at but I have the .blend if someone wants it.