Are all colors of DME equal in sugar content? Is there a difference in flavor between them or is it strictly a color difference? Could you prime with dark DME, then?
The darker extracts have some specialty grains mixed in with the base grains to get the darker color (typically crystal and chocolate malts). The total contribution of fermentables should be identical but it might change the character of your beer.
I had the impression that the amount of sugar used to prime is so small (relative to the batch size as a whole) that it wouldn't make a lot of taste difference what you primed with. I bet someone on here will have tried different kinds, and I'd be interested to know if they think the difference between DME types would be detectable in the flavor.
i bottled a stout, half using priming sugar and the other using Dark DME. honestly i can't tell much of a difference, the one with DME may have a darker head to it.
just remember its not equal as far as amounts go. there was a chart i used online that gave how much corn sugar/ DME / Honey could be used to prime with.