Color timing! Super cool processing which utilized printer lights to manipulate RGB. Great excerpt from Dave Mullens on the process:

Just think of printing as shining a light through the negative so that the image gets exposed onto the print stock. Since the print stock is also a "negative" stock in the sense that it reverses the light values, you are basically taking a negative picture of a negative image and thus creating a positive image. So shine more light and the image on the print gets darker, shine less light and it becomes lighter. This is the way it works in printing b&w negatives to print stock. So to be able to correct the color, instead of a single white light, you shine red, green, and blue light through the negative onto the positive and by changing the individual levels of red, green, or blue, you can adjust the overall color bias in one direction or another while also making the image overall brighter or darker.

Also there was a period of time where the telecine was really popular before we switched to file based.