 <?php
//* Do NOT include the opening php tag shown above. Copy the code shown below.
 
//* Add custom body class to the head
add_filter( 'body_class', 'sp_body_class' );
function sp_body_class( $classes ) {
	
	if ( is_category( '1' ) )
		$classes[] = 'custom-class';
		return $classes;
 
}

	<?php
	//* Do NOT include the opening php tag shown above. Copy the code shown below.

	//* Add custom body class to the head
	add_filter( 'body_class', 'sp_body_class' );
	function sp_body_class( $classes ) {

	if ( is_category( '1' ) )
	$classes[] = 'custom-class';
	return $classes;

	}