This is the beginning stages of a 1955 Cadillac illustration (colored pencil on mat board).  Prismacolor brand colored pencils were used.

The car was the main focus of this illustration so I started by sketching that in first. Second, the house was drawn in.

Once all of the elements of the portrait were in place I started rendering in the sky using Deco Blue and White. All of the many mistakes are corrected in the pencil stage prior to adding color.  

The base layer of pencil in the lawn is Limepeel (a very light yellowish-green). Then a layer of Celadon Green to subdue the yellowish tone a bit. To add to the perception of depth, I've darkened the lawn in the foreground with layers of Marine Green and Dark Green. These same colors were used to create the trees and shrubs.

The street was filled in using 20% Warm Gray. Same with the driveway, but I applied the color a bit heavier. This makes the driveway surface seem smoother and slightly darker than the street.

 
To render the car's shadow, I used 50%, 70% and 90% Cool Grays - 50% Cool Gray on the outer edges, blending into 90% Cool Gray beneath the car. 

I'm starting the chrome using a White pencil to render the areas that will brightest. Once I've determined where all of my brightest areas need to be I begin filling in the car's grill with Black.

Lets not forget that house back there - The brick is a blend of Terra Cotta and Burnt Ochre. The wood trim is Dark Brown and the Stucco portion is Cream. 20% Warm Gray for the roof.
The same 20% Warm Gray used on the street will be reflecting up into the lower portions of the bumper. Portions of the headlights will reflect the 20% Warm Gray as well. Also used in the headlights are Deco Blue (reflecting some of the sky) and a blend of 90% Warm Gray and Marine Green which is the horizon line reflected in the chrome.
The grill and bumper are starting to take shape. Notice the headlights and portions of the grill being reflected into the bumper bullets.

The front wheel has been started - The tire is a blend of 50% and 90% Warm Gray. White for the sunlit portions of the whitewall and 20% Cool Gray for the shadow portion of the whitewall.
The hubcap has been rendered in using the same principles as rendering the chrome bumper and grill. That chrome hubcap will reflect all of the colors around it - in this case, various shades of Warm and Cool Grays, White and Deco Blue.
Here I slowly render in the contours of the fender. Again, I start by putting a layer of White pencil where I know the sun will reflect off of the paint.

The first layer of color used was Light Green.
Over the first layer of Light Green I applied an equal amount of Deco Blue - This provided the basic overall color of the car. After the base color has been achieved I develop the contours and shadows by layering Light Aqua, Aquamarine and Parrot Green. The actual shadow areas under the headlights were achieved by blending in a bit of Cool Gray (maybe 50% Cool Gray).
Here I'm working my way back across the hood in the same method.
Just workin' my way back.

Notice how you can still see pencil strokes especially in the darker areas of the hood - I'll get rid of that later.
Here the windshield has been rendered in. As usual, I started by rendering in with White pencil where the sunlit portions of the glass were to be.
Here the lower-body contour where it curves in has been rendered using Light Aqua, Aquamarine and Parrot Green.

Notice the White pencil was used to begin rendering the top portions of the fender - that white area begins above the headlight and will travel all the way back to the tailfin.
The rear wheel details have been added. Compare this photo with the one above and notice how adding the chrome details of the roofline gives some depth perception.
Here is the final product.

One of the final steps is to use Prismacolor's Colorless Blender. This was only used on the car to smooth out the visible pencil strokes and give the paint that smooth, shiny appearance.