WordPress Customization API overwrite LESS variable

LESS happens as a preprocessor and doesn’t render dynamically each time your page loads. So, you write your LESS, compile it to CSS, and then load the CSS in your pages.

There may be ways around this, but you would probably be better off using targeted CSS with classes to create the CSS on the fly.

add_action( 'wp_head', 'do_custom_css' );

function do_custom_css() { 
    if ( $custom_color = get_custom_color() ) {
.some-class {
    color: {$custom_color};