Invert/Negative textures behind actor

I have a regular sphere actor with transparecy that have to invert colors of everything behind itself. How can i do this? I have tried post process - yes, it works, but it affects all of the screen, not exact sphere.

the scene color node can be used instead of the scene texture nodes and will work on a surface shader. alternatively you can set the sphere to render custom depth and use custom depth as a mask in the post process.

I don’t think the first option will invert the colors of transparent objects, the post process/custom depth will depending on where in the render order you set it to be applied.