[mcphage]

> The fabric ribbons are fitted with a retroreflective strip for homing. This gives us one absolute starting point on each pixel and then each color is just at a fixed ustep offset from zero.

If you had a reflective strip between each color—and just counted the strips to determine current color—wouldn't that have kept it in continuous calibration? Then you wouldn't even need a stepper motor, you could use a plain DC motor, since you wouldn't be using the step count to determine position anymore.

(I haven't used that setup for a real project, but I intend to since it seems it would be cheaper and easier, and I was wondering if you considered something like that but dismissed it.)

Also, if you don't mind sharing: what IR sensor did you use?