Hello, thanks gentlemen , I appreciate the comments.
Rick beat me to the answer, so I wont cover that again
For the color variations ,the first thing I did was use different colors of primer. example: the side skirts, the darker ones were primed with black, lighter ones with grey. For even lighter ones use white primer. After applying the base coat of dark yellow, I added white and a hint of light flesh tone to it for the highlights. For darker tones I added Vallejo golden brown to the dark yellow. you can achieve many variations of dark yellow using different colors or different amounts. Most of the time I wont do all these variations in tones, but with the monotone color , I felt it needed some added "oomph" to keep it from being a bit boring.
For the paint chipping I used a Scotchbrite cleaning pad (the green one) just cut off a corner, dip it in your paint , dab it on your cleaning towel, and then press away on your model in various areas. I use that for general application, and then a tiny brush for the precise areas.
Hope this helps anyone ,thanks for the compliments guys