selecting multiple layers at once

ok, im in photoshop 7. i added bodykits to the car and they are as seperate layers. i want to change the color of the car with the body parts i added at the same time. so i want to know how do i select multiple layers at the same time so i can change the color of all the parts?

I'm not sure how to select multiple layers, but I like to make a "master layer" over top of all the other layers. First, I make duplicate layers of all the other layers and desaturate the colors. Then I match the colors as best as possible and merge all the duplicate layers using CTRL+E. The new layer is colorless and has all the parts in one image. By placing this layer as the first layer, it can be erased to reveal colors underneath (for windows, lights, door handles, etc.) and can make the whole car have a uniform color without matching all of the seperate layers.