Question / Help Black & White + one color

[CloodStool]

I'd like to set up my camera so that it's in black and white except for anything that is red (think Sin City)
The closest thing I've found is color correction but that only seems to add a red filter on top of the image, which isn't exactly what I'm looking for.

 

[HomesBones]

Hi, I just found out how! Use the Chroma Key and choose the color you want to remove. Max out the Key Color Spill reduction and play around with the Similarity and Smoothness Sliders (mine are both on 1) and duplicate that filter for every color you want to remove out of the scene except red / magenta. Hope it helps!