Generated by SassMeister.com.

input.scss

@function con($color, $light, $dark, $threshold: 51) {
    @return if(lightness($color) < $threshold, $light, $dark);
}

a {
    color: con(#fff, #abc, #cde);
}

output.css

a {
  color: #cde;
}

settings.json

{
  "sass": {
    "compiler": "dart-sass/1.32.12",
    "extensions": {},
    "syntax": "SCSS",
    "outputStyle": "expanded"
  },
  "autoprefixer": false
}