Shader HDRP using shadow information

Hello!

I'm new to shaders and I have this project where I would like to have some sort of post-processing effect in HDRP where let's say shadows become color A and lit areas become color B.

Is this something that is possible to do with shaders? Is there a way to get from the screen position, wether or not that point belongs to an object that is lit?

Thanks for any help,
Cheers