Looking at the Drivers Information Center over the steering wheel (assuming the truck has one) I would look at both the mileage and the total hours. Helps to evaluate if the truck has been driven over the road or in town, idled a lot, etc.
You want to make sure the fuel filters have been changed on schedule, or even better, a secondary filter installed (I don't know, outside of fanatics like on this website, how knowledgeable the general Duramax public is about the need to keep dirt out of the injectors.). Get a service history.
The Duramax comes with either a 6 speed manual ZF, or the Allison. Nothing else. If you have bucket seats and a center console, only the Allison. Not many stick shifts out there.
I cannot tell you about the colors.
You want to make sure the fuel filters have been changed on schedule, or even better, a secondary filter installed (I don't know, outside of fanatics like on this website, how knowledgeable the general Duramax public is about the need to keep dirt out of the injectors.). Get a service history.
The Duramax comes with either a 6 speed manual ZF, or the Allison. Nothing else. If you have bucket seats and a center console, only the Allison. Not many stick shifts out there.
I cannot tell you about the colors.