@Sven Thanks
Yes, I primed them white so that I would not have to cover black with my red or yellow. Maybe it is a combination of them being to dark and the wrong wash (tried black and D.Mud and was happy with neither). It was just that I planned the stripes to be brighter.
I though about masking tape, but then I remember that the stripes must look straight from 1 meter away, so I scraped the idea.