don’t have the details at hand, but they were standard osram
fluorescent tube dimmers.
Whereever they sell dimmeable fluorescent tubes, they will also sell
the dimmers that go with it.
they took 0-10v, if i remember correctly.
I wouldn’t recommend DIY as this is high-voltage and fluorescent tubes
seem to be a science in themselves..
tubes have fixed colours, yes, but there are balanced red, green and
blue tubes around made for additive colour mixing.
circular tubes of changing colours sounds like rgb led-strips, lots of
different types of those coming out now..
I had a friend build a custom device for 8 TL tubes for me, using a
Doepfer MIDI-to-analog unit controlling a bunch of relays. If you’re
dealing with tubes that are 40 watts or less, it would probably be
cheaper to build something which controlled relays, rather than
dealing with pricey dimmers.