Make the bridges change the road's colour.
In medieval periods, most roads were packed dirt (mostly packed by the carts and horses travelling along them) and a rare few were paved stones (mostly Roman Leftovers). Some nobles would add coarse gravel to their packed earth roads, to make them more traversable during the wet.

So, keep your "mostly sand yellow" roads out in the countryside. Change the road to a grey (possibly cobblestone) colour at the bridge. Back to sandy yellow and then use maybe a subtle 5-10% grey inside the city. It will give the impression that the city roads are mostly stones, and the same for the bridges. Alternatively, if you have timber bridges (significantly cheaper and easier to build by hand) then use a suitable brown.