That is weird. It looks like grease or oil. I'd be checking the fork seals and perhaps the front wheel bearings too.
I've had brake dust on my wheels before and it doesn't look like that. Normally it's an even film of dust that wipes off easily. Unless that's after you've tried to clean it with something and it's smudged?Like TwoWheelWonder mentioned it might just be break dust. There was a little on the rear also.