C1's film grain tool is the most accurate, native tool I've found in any photo editor software, but it's lacking the last part of the emulation of film grain that occurs in color film stocks, which is the "natural color microdistortion" caused by the colored dyes that get exposed while photographing.
Some people like it, some people don't, but it is a characteristic of color film and it'd be nice to have the option to dial it in.
I don't know how to explain it better but I've seen that, for reference, Dehancer has that slider.
+1
This already exists in hasselblad phocus.
Would be really really nice to have a colored noise, with a "saturation" adjustement in the grain tool.