playing around with phantom frog i found another solution:
let's take the same situation, blue scene, fading the fixtures to the audience, changing color to white, so
1. put the blue scene to a memory, let's say no. 50
2. put the blue and white scne to next memory, no. 51 in this example
Then flash your memory 50 (ok, no flash button, but the fader should work, too ) and then press "GO"
And if you don't like "flashing" via fader, start with (empty or let's say "dark") memory 49 (and get Memory 51 to jump to Mem 49) .
So open memory fader, memory 49, hit go -> blue scene, hit go -> blue scene moving to blue and white scene, hit go -> darkness. Don't forget to play around with fade times ... Cool ha?