sanitize_hex_color()

sanitize_hex_color( string $color ): string|void

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;
	}
}