Have you seen this? Green screen on crack.

https://m.youtube.com/watch?v=UQuIVsNzqDk

That and more really. You could use it to do a green screen effect, but you can also use it to adjust color balance, brightness or do weirder things like swapping values between colors. It gets really crazy when you are working with full video because the time of the current frame is also available to be incorporated, so you can even do animated effects.

Another powerful filter is the convolve filter. That allows you to apply matrix transformations, which can for example be used to apply a homography matrix and adjust a videos perspective.