I once achieved this effect (Three horizontal colour stripes on the
Cyc) by first using a ground row to wash the cyc up in my base colour. I used barn doors to cut off the light from the floods at a bit above the right height .
Then I put
ERS lanterns on booms each end of the cyc and on an overhead bar pointing down pretty steep (about 60deg) in my middle colour washing out the base colour and using shutters to keep the edges sharp.
My top colour of the three was in floods from above, once again with barn doors cutting them off about 1/3rd down.
The light from the ERS's in the middle was strong enough to cut across the top and bottom giving nice crisp lines between the colours with no bleed. The ERS focus was very difficult and did slip no matter what we did so checking that was a nightly task for the ME before the show opened. I had to be careful plotting in order to achieve the effect without one of the colours appearing brighter as well, but that is stating the obvious.
You should now completley ignore everything I said. I just realised the french flag is vertical stripes not horizontal. I am a complete idiot. Well on Saturdays anyway.