Transparency and RGB support to colour picker

Colour picker should support also transparent background-color property - theme designers often want to use background-color:transparent instead of some color.

If you add to lib/adminlib.php class admin_setting_configcolourpicker extends admin_setting

/ protected function validate($data) two lines

} else if ($data=='transparent') {
return $data;

so that the validitation could be done with

protected function validate($data) {
if (preg_match('/^#?([a-fA-F0-9]

)

$/', $data)) {
if (strpos($data, '#')!==0)

return $data;
} else if (preg_match('/^[a-zA-Z]

$/', $data))

else if (empty($data))

else

}

This way theme administrators can write value

transparent

to colour picker input box and it is accepted as valid background-color.

Transparency should of course be used only for background colors (not for text colors) so it could be good to note in docs or some help file about this thing...