Several of us have tested and found that even amber LEDs can work fine at surprisingly bright light levels. I can even use mine for colour if I turn it right down to a level that I can just see the image come up in the tray with dark-adjusted eyes. Safe time at the trays is only 2 minutes though so I keep the paper shaded most of the time and turn the wick down further.
Mine is just a metal box with an adjustable current source for the LED. Power is from the usual type of plug-in dc power supply. The only slightly unusual thing is that I have LEDs soldered to 2.5mm dc power plugs and the box has a corresponding socket so I can plug in different LEDs. In retrospect, the variable current is over-kill as I only ever use it full blast when doing b&w - colour could be taken care of by simply shading most of it it with black paper. A simple power resistor would do almost as well...
I uploaded a pic in another thread: http://www.apug.org/forums/attachmen...8&d=1132187903
and attached a close-up below.