There's no setting on the Simpsons Avatar creator for slightly greying.
Actually, the Simpons Movie website is incredibly well designed.
Yes, it is a Flash site but that works with the fact it is an animated film and not against it like so much use of Flash.
I think I need to bring this into Photoshop and make my other adjustments.
The avatar creator didn't have a "slightly greying" setting nor did it have "aging and soft" as a body type.