Here's a quick and easy to use shader that will replicate the Sin City aestethic effect, the desaturation with over contrast, and of course, the trademark "only the red colors display"
This shader is extremely easy to use. Just write shader_sincity_start() or shader_sincity_start_extended() and you are good to go.
For more information, read the readme in the notes section!
Here's a demo of the shader working, allowing you to change different parameters
Hope you enjoy!
Contact mail: firstname.lastname@example.org