Hey Lulighttec-
looks like you got the owners into a decent budget. good for you!
in order to do this, you will also need Dichros and dichro mounts. software/hardware. i would suggest the QuickShow package that we spoke of previously.
The way the lasers mix colors is by analog modulation (or TTL. but TTL is very uncommon these days and not preferred). By varying the output power of each laser from 0-100% in turns translates into color mixing. Each laser is controlled by the voltage input. 0V= no output. 5V=Max. output. and then everything in between. so by changing the input voltage on each laser you get approx 16 million color combinations.
-Marc
feel free to give me a call again if you have need more info or have more questions