You have two/three options if you want to accept colors within your matched text. You can use a regex to strip out the codes in the event header, use a wildcard (non-regex) event and strip the colors inside the event, or turn off color codes completely in mIRC. And if I understand correctly you want to allow for an arbitrary number of spaces between words? Tokenize will take care of that, or a \s+ in the regex.

Code:
on $*:text:/\?throw\s+at\s+(\S+)/S:#:{
  if ($regml(1) !ison #) return
  ;start here
}

on *:text:*:#:{
  tokenize 32 $strip($1-)
  if ($1-2 != ?throw at) || ($3 !ison #) return
  ;start here
}