@function colour-difference($foreground, $background) {
$r: (max(red($foreground), red($background))) - (min(red($foreground), red($background)));
$g: (max(green($foreground), green($background))) - (min(green($foreground), green($background)));
$b: (max(blue($foreground), blue($background))) - (min(blue($foreground), blue($background)));
$sum-rgb: $r + $g + $b;
@if $sum-rgb < 500 {
@return "false";
} @else {
@return "true";
}
}