ActionScript 2.0 :: Color Object Prototyping?

i've been using a MovieClip prototype to create and set a color object, like this:

MovieClip.prototype.setRGB=function(hex){
(new Color(this)).setRGB(hex); //creates color object + sets color
}

which makes it easy to change a MC's color like this:

MC.setRGB(0x00ff00);

now i'm working in AS 2.0, which seems to discourage using prototyping and extending the MC class methods--so my question is, what is the best approach for doing this in AS 2? i've created a new class to handle it, but it seems clunky to have to call an instance rather than having a MC call an internal method...the bottom line, is: is it ok to extend the MovieClip class in AS2, and if not, what's the cleanest approach?