Make camera black and white but keep one color?

I want to make my camera view to be black and white but keep all red color colorful. I want the game to look like the tagged image below:134054-image.jpg

Can I achieve this by accessing the post-processing effects or via editing the camera view as I want this to work on a web camera in the real world as well as in the actual game?

You can do it with a custom shader.
Sin City Look using HLSL

UPDATE : I also make some tries with PostProcessing-ColorGrading. I changed the Channel Mixed and set Red Channel to (0,2,2), Green Channel to (0,2,2) and Blue Channel to (0, 0, 2).

UPDATE 2 : I’ve acchieved better results with Hue vs Sat Curve
. Check this configuration.