Since I've only owned 901's and on 901's it is possible. Problem is that it would require a VERY steady hand and a soldering iron the size of a needle. The LED on a 901 appears to be a SMD LED. Here's a picture of the rough size of the thing, TINY! It'd be much easier to either by a batt with the correct color already built-in or to use something (like gel film or different ashcap) to change the color of the built-in LED.
Just my $.01
AND THAT'S A FRIGGIN' DIME! Which is about DOUBLE the diameter of a 901!