alias colour {
%x = $+ $1 $2-
return %x
}
//say $colour(04, see the result here)
(Note: I used $colour instead of $color on purpose since $color is already an identifier)
Edit: $color and $colour are interchangeable existing identifiers, but you can override one of them in this way, with the alias, while still keeping the other. You may choose another alias name too.