You can use either gdscript (think python) or C#. C# used to be a bit of a second class citizen but from what I see it’s nearly on par with gdscript for support, and it’s getting a lot of attention from the devs.

Edit: and yes there is a post processor

Yeah there is post-processing and shaders as you'd expect. I forgot to mention that I use GDScript, it fits in with the engine way more intuitively, not to mention C# support is lacking in a few things.