It's less that they changed and more that the puzzles up to that point make you jump to that conclusion, and that puzzle is there to break that assumption. But I got stuck there for quite some time too until I took a long pause.
Didn't solve yet, but I'm assuming thatsince the next floor is green, you need to find out what colors are each tiles by the blue/red floors, and then see how the colors would be reduced to in the green one.
I did it a few moments after posting, but thanks....admittedly I kind of guessed and it worked lol, I feel bad now.