I have some simpson's chocolate malt left over from another batch. Can I steep 4-6 oz of it as my specialty grain in my NB dunkelweizen extract kit to give it some darker color or will it give the beer off flavors.
Generally off flavors refer to a beer getting infected, in that regard no, not at all.
I put chocolate malt in similar amounts(1/4 lbs) into brown ales. It will impart a bit of flavor but it should be pretty subtle. From my experience this will darken a beer and give it a slight nutty flavor. Not out of place for a dunkle.
Assuming you're referring to a 5 gallon batch of course.