I'm going to taken the
incandescent option and say built light boxes, sand the plexi to diffuse it, paint it what ever color you want, and stick two 100w light bulbs in there. Control with your floor dimmers if you have some.
^^^ Just to add (my 2 cents worth) to this...
If you're building custom boxes or stair treads, and the
effect you want is for each tread to illuminate when someone steps on it... I say automate it.
Use a piano hinge or something along either the front or back
broad edge of the step. Leave the other end floating. Place a limit
switch inside the light box. (Similar to the "stomp switches" on guitar pedals, but get a
momentary switch, not a latching.)
Wire the lights through the
switch -- they're usually rated at least 5A, which is plenty for a pair of lights, and overkill for LVDC like LEDs or EL strips.
When the performer steps on the tread, it'll depress the stomp
switch, automatically closing the
circuit to the respective step light. When they step off, the
return spring will pop the
switch back to the "OFF" position and shut off the light. The
edge of the tread would only need to move about 5mm or so, which no one... not even the person walking on them... will notice.
This also frees your lighting operator from having to closely watch the performer's feet and manually sequence the lights. It also frees up your lighting control channels, as the whole
system would be fully automatic. It also reduces the number of electrical wires running across your
stage -- only 1
cord needed for the whole staircase, rather then a
cord for every step of the staircase.
