When I painted them, I put a solid coat of anthracite grey over the base. The next step was to cut some strips of blue tape so I could get nice straight edges. I stuck the strips down and painted a bit of white onto the base. For the yellow stripes, I put a coat of yellow over the white.
In the end, these turned out very nice. They do look a little like they are all walking down the middle of the road together, but I'm okay with that.
Let me know what you think or if you have any questions.