diff --git a/phpBB/includes/acp/acp_groups.php b/phpBB/includes/acp/acp_groups.php
index 089fe4baa1..83c355540e 100644
--- a/phpBB/includes/acp/acp_groups.php
+++ b/phpBB/includes/acp/acp_groups.php
@@ -421,7 +421,7 @@ class acp_groups
 					*/
 					$validation_checks = array(
 						'max_recipients' => array('num', false, 0, 16777215),
-						'colour'	=> array('hex_colour'),
+						'colour'	=> array('hex_colour', true),
 					);
 
 					if ($validation_error = validate_data($submit_ary, $validation_checks))
diff --git a/phpBB/includes/functions_user.php b/phpBB/includes/functions_user.php
index f8e1fcaa45..61972c3876 100644
--- a/phpBB/includes/functions_user.php
+++ b/phpBB/includes/functions_user.php
@@ -1903,14 +1903,16 @@ function validate_jabber($jid)
 * Validate hex colour value
 *
 * @param string $colour The hex colour value
-* @return bool|string 	Error message if colour value is incorrect, false if it
+* @param bool $optional Whether the colour value is optional. True if an empty
+*			string will be accepted as correct input, false if not.
+* @return bool|string Error message if colour value is incorrect, false if it
 *			fits the hex colour code
 */
-function phpbb_validate_hex_colour($colour)
+function phpbb_validate_hex_colour($colour, $optional = false)
 {
 	if (empty($colour))
 	{
-		return false;
+		return (($optional) ? false : 'WRONG_DATA');
 	}
 
 	if (!preg_match('/^([0-9a-fA-F]{6}|[0-9a-fA-F]{3})$/', $colour))
diff --git a/phpBB/includes/ucp/ucp_groups.php b/phpBB/includes/ucp/ucp_groups.php
index 20a55d8c32..9365913541 100644
--- a/phpBB/includes/ucp/ucp_groups.php
+++ b/phpBB/includes/ucp/ucp_groups.php
@@ -596,7 +596,7 @@ class ucp_groups
 							}
 
 							// Validate submitted colour value
-							if ($colour_error = validate_data($submit_ary, array('colour'	=> array('hex_colour'))))
+							if ($colour_error = validate_data($submit_ary, array('colour'	=> array('hex_colour', true))))
 							{
 								// Replace "error" string with its real, localised form
 								$error = array_merge($error, array_map(array(&$user, 'lang'), $colour_error));