Well thats easy enough, in my example the changed code would be:

alias colorit { if ($isid) && ($1 isnum 0-15) && ($2 isnum 0-15) { return $iif(b isin $prop,) $+ $iif(u isin $prop,) $+  $+ $iif($1 isnum 0-9,0) $+ $round($1) $+ $chr(44) $+ $iif($2 isnum 0-9,0) $+ $round($2) $+ $3- $+ $iif(b isin $prop,) $+ $iif(u isin $prop,) $+  } }

That just uses the same $iif's that set the b or u to unset them and throws a control+k at the end instead of the control+o.