Paint.NET :: Change Color On Digital Drawn Picture?

I'm a Model Railroader, as the screen name implies. "RRArtist" RailRoad Artist. Anyway, I have a MoPar garage, planned, I have this 3D model, built, I'm merely working on a sign, that is based off I think the 1950's.....This sign, will depict my interests in MoPar, a "Hemi", and the classy girls used back in the day, as part of the sign, AND will be lighted......SO, in 1/87th to the foot scale (Pretty small) its nearly impossible to get a "Hemi" motor, and be able to see that it is a Hemi! SO, my plan, is to take a 1:25th scale Hemi motor, and mount it to a sign pole, that's a pipe, to carry wires for lighting. Then UNDER this sign, will be a girl, that looks as tho, she is holding up a sign that says "Hemi" in the old "MoPar" signage.....UNDER her will be this Hemi Motor.....BUT the lighting is the fun part as the "lamp shades. will be CHROMED Hemi Valve Covers.....With the motor itself, painted orange, with black valve covers.....
 
Now this girl on the sign, is the issue.............. The girl is actually a blonde.....(don't ask LOL) I need to change her hair color... to red! Problem is? The clothing shes wearing, a short skirt, or short shorts, that are also...........RED.... so, it leaves way to much "red" for the sign......Looks good as is, don't get me wrong, BUT, if I can replace her blonde hair with red hair, to match the "looks" of the image, to be "believable" is GREAT, BUT I want to remove the red from her clothing, and make it Hemi Orange.......... trimmed in black with the silverish looks it already has, blended into the red as you will see...
 
This whole project is going on a display I'm adding to my layout for looks for when I run trains and to show my other interest.......... old MoPar muscle cars that were Hemi with a garage to repair them, from back in the day......Trying to make all the colors fall into place is my issue!