This package only provide a single function that return a contrast color using CIEDE2000 algorithm. Usage: (contrast-color "#ff00ff") ; -> "#1b5e20" or (contrast-color "Brightmagenta") ; -> "#1b5e20" Note that as default color candidates, this package uses ‘contrast-color-material-colors’ variable, which is defined based on Google’s material design, but if you want to change this color definition you can do like this: (contrast-color-set '("black" "white")) But keep in mind that providing many colors may increase calculation time.