I haven't busted out my Boba Fett reference CD in a few years, and just recently have been studying things in there again, and that ROTJ jumpsuit on the mannequin at Magic of Myth is definately a light blue, the exact same shade as the reference pics of the ESB jumpsuit. It looks like they just weathered it heavily to give it that "gray with a hint of tan" look. I know Braks Buddy was using a very high quality camera and took those pics in high res, so the colors aren't off. It's a light blue jumpsuit. Just look at many of the photos in different areas of the suit and in so many of those shots, the spots they didn't heavily weather show clean light blue fabric. Especially spots they didn't think they had to weather, like upwards shots under the shoulder bells and inside the thigh pouch, where the corner is opened up a little and you can see the clean inside fabric underneath. Light blue all the way. Also right at the bottom of the legs, they weathered the lower legs heavily, but because they had to put the metal mannequin attachments up the calves, the spats don't cover the bottom like they normally would, and again it looks cleaner than the heavily weathered calves, and you can see that hint of blue at the bottom of the legs there, too.
Now I have an ESB bluish jumpsuit that I weathered down that I've worn with my ROTJ costume for years and I can see I'm not off with the M.O.M. suit, in fact it might be more accurate than the majority of ROTJ costumers that base their suits off the M.O.M. suit and buy gray jumpsuits.