These things have started popping up everywhere lately.  I first encountered them in the cafe/lounge area in the Student Union of RGU in Aberdeen, and was instantly captivated...and I wanted to go and start pulling the lamps out of the ceiling to get a better look!  Walked in, they looked purple - all of them...but were all casting a vivid coloured spot on the floor beneath them...in blue, yellow, red, pink and green...Three years on, I finally spotted some in Maplin.  Will get some more colours later.

It's a very normal low wattage low voltage dichroic MR11 halogen lamp from a technical standpoint.  What makes it somewhat special however, is the coloured filter applied to the lens.  I've seen several cheap knock-offs of this type of lamp, which just use a coloured lacquer on the lens.  It works, but tends to flake off and fade.  This however seems to have a proper dichroic coating.  You can tell that because the actual colour of the filter appears to change depending on the angle you look at it from.  Reflections too seem to have a very distinct yellow colour to them.  It is really very, very pretty to look at...hence that this lamp has been sitting on my desk for the last day and a half.

This one's not the best made one I've seen.  The bulb itself isn't well centred in the reflector at all, as a result the beam's rather lopsided.  It is however a lovely colour.  The beam centre is a deep saturated blue, fading to a slightly pinkish corona.  The package states the beam angle as 10 degrees, I'd say it's closer to 20 though.