Is it possible to control the intensity of a channel using the color parameter of another channel?

As a preface, I have no need for this actually to work, but it would be interesting to see how this would work, should it be possible.

This idea may be hard to explain but here goes: My venue has a cyc with three conventional fixtures pointing at it, each of these fixtures is comprised of three smaller conventional fixtures that have red green and blue gels on them. 

Would it be possible to have a master channel, where, changing the RGB value of this master channel, would change the intensities of each of these sub-fixtures to match?

Is this feasible? I tried to do something with multi-cell fixtures, but I couldn't get it to work.

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