Thought I'd do another quick tutorial. Many colour grading applications have a function similar to the RGB Mixer in DaVinci Resolve but they're often overlooked. This tool got me out or trouble a while ago. I tried the usual things, including changing the raw .r3d settings but I ended up using the 'fettle' curves on a Quantel Pablo which is where their version of the mixer is - the principle is identical though.
I hope this is a useful tip. I may do another tip soon...
You can see the rest of my old reel here https://vimeo.com/channels/420531/3940421
(Sorry about the sound quality on this, I may redo it if I can get my headphone mic to work!)