man your improving alot, keep it up man, the more you produce the more experience you get
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To make the rims black, first select the part and then proceed to desaturate, then go to Contrast/Brightness and play around with those settings, it usually turns out that you usually have to lower the contrast to black out the rims.
To be serious, the truck color change is very good, not many people can cover the orange teh way you did, well they can but most never do, that shows that you have very good selections.
Keep it up man.