Converting to LAB would give you access to the Delta E formulas. I wrote an introduction to dE here, if you're curious: http://zschuessler.github.io/DeltaE/lea

Converting to LAB would give you access to the Delta E formulas. I wrote an introduction to dE here, if you're curious: http://zschuessler.github.io/DeltaE/learn/ http://zschuessler.github.io/DeltaE/learn/ Check out the demo page as well, if you're on desktop: http://zschuessler.github.io/DeltaE/demos/de76-chroma-key/ http://zschuessler.github.io/DeltaE/demos/de76-chroma-key/ The repo is public domain. Hack around with the library if you'd like!