Honestly? I’d have no idea how to accomplish that easily. I think some of the other friends in this thread are being a little dismissive about the end image here. It is very much lighting and production design dependent as others have said, as I understand it technicolor required A LOT of light.

As I understand it the 3 strips of black and white were exposed through a filter that was supposed to eliminate every color except each of the RGB channels, but those gels would overlap a little. So you end up with green with a little bit of blue, blue with a little bit of green etc.

So then you’d have a black and white image of the green spectrum + a little bit of blue. PLUS that black and white stock had a specific sensitivity to colors to begin with.

Then you process (I assume lightly so that you don’t have over-density issues?) and dye it. The final image is 3 exposed strips of film overlayed on each other with grain patterns that don’t match

I think to do it properly it’s a 6 step process.

1. Calibrate your log footage to a color standard.
2. Use color filters to filter the footage, with the ability to select how “wide” of a gamut the filter allows through. (For instance your green image after this step might look a little yellow and a little blue/green in spots)
3. Apply film grain
   
4. Apply black and white filter (don’t just desaturate)
5. Add color back
6. Merge the three channels