Weird Coloring on Car

I’m working on a design to test in OpenFOAM, and because of this, I haven’t messed with materials at all. I messed up extruding, then selected it all to remove the doubles, then tried again. However, I forgot to deselect it all so it ended up extruding everything. I undid this and removed the doubles again, however everything looks really weird now. About half of the faces are a different color. I have tried messing with materials, and the problem is still there. I guess it doesn’t matter that much because I am mainly concerned with the shape, but it bugs me and makes it harder to see the shape. I am fairly new to blender, so that is why I am asking for help. Any aesthetic/aerodynamic changes/suggestions are welcome as well.try III.blend (720 KB)

You’ll see that you have some faces pointing outwards and some faces pointing inwards

Select all faces and recalculate their normals with Ctrl+N