Five of the striped blocks have a paler color on the outsides (mostly pale yellow), while the other 16 blocks all have deeper tones on the outsides. As others noted, the pale yellow doesn't contrast as much with the solid white blocks, so I might have all the pale yellow blocks go upright. As it is, your colors are really neat for a small child. I'm not sure how you could follow Zone's idea of roads, but it is an intriguing idea for a little guy.