A cassette containing a gel scroll is releasably attached to the forward portion
of a housing of a luminaire. A light path through the cassette is aligned with
a light exit opening of the luminaire. A gel scroll is wound upon a pair of drums
in the cassette and intersects the light path. The drive motor for the cassette
is contained in the housing of the luminaire. A drive system for the drums includes
a driven member in the cassette that engages a drive member of the luminaire driven
by the motor when the cassette is mounted on the luminaire. A fan in the luminaire
moves cooling air through the cassette when the cassette is mounted on the luminaire.
