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function is not described

sanitize_hex_color() WP 3.4.0

Sanitizes a hex color.

Returns either '', a 3 or 6 digit hex color (with #), or nothing. For sanitizing values without a #, see sanitize_hex_color_no_hash().

No Hooks.

Return

String/null.

Usage

sanitize_hex_color( $color );
$color(string) (required)

Code of sanitize hex color: wp-includes/formatting.php VER 5.0.3

<?php
function sanitize_hex_color( $color ) {
	if ( '' === $color ) {
		return '';
	}

	// 3 or 6 hex digits, or the empty string.
	if ( preg_match('|^#([A-Fa-f0-9]{3}){1,2}$|', $color ) ) {
		return $color;
	}
}