Okay, so I am making a mesh and I'm not sure how to make it recolorable. I am basing it off of the Fender Jazz bass, and here's a picture of the original Sims 2 image file:

How do I edit it to make it recolorable? I've completed the mesh conversion in Milkshape and now I'm editing the image files. And what are all the squares and rectangles for? (Like the ones next to the guitar and to the right of the neck)
Don't worry about the strings. I've already made a seperate image file for them.
I'm only making the body recolorable. I don't need to make the neck recolorable, so why put in the extra effort to do so?

What squares and rectangles are you talking about? I don't see any.

To make it recolorable you could just desaturate the image and play around with the curves and levels till it looks right. As for what certain things are for you'd have to check out the UV map for that, I would suggest loading your model in milkshape and applying the texture to it. You might as well do this anyways since you now have to make the mask texture from scratch, the UV will come into play when mapping that out.

Still puzzling over what you meant earlier...But, yeah, desaturate the image, and make it your multiplier. Then copy it and set up your mask. The mask, the red/green/blue image that you see in S3 files, is what controls recolorability. Each color is a different channel. Make sure the colors are true red, blue, and green, or your image won't look right (e.g., 255 red, 0 green, 0 blue is true red). If you only want one recolorable channel, use a solid red mask. For the strings, etc, you'll need to use an overly, since you didn't want to make them recolorable.

Hope that helped!

the squares and rectangles your talking about are the sides of the neck and the sides of the gitar