You could use the * to match style="" if you like. Having thought about it you don't really get spaces in attributes but in the style attribute you do get : and ; which my fist expression will not catch.
Try style="[^"]*" (if you want style="" to be caught) or style="[^"]+" (if you don't) instead. These ones will catch spaces but they will also catch more than just alphanumeric words as well.