Match the most prominent/important colour and the overall density/contrast saturation and then use broad HSL keys for 1-2 other main colours.
I’m working on creating conversion LUTs between 8 different film negative stocks, the Red Epic, Arri Alexa, F65 and C300. I shot a 13 stop range of 142 colour patches in both tungsten and daylight lighting to do this so they should be very accurate. They’ll be ready in 2 months guys (-;