1) How wide do you want the road to be?
2) Pick the lightest and darkest colors you would like for the road.
3) Pick a few transition colors between those two light and dark colors.
3) Create a ruleset for how you want those colors to be painted so that the transition between colors looks correct. Mainly you need to focus on what colors you want painted directly next to another color, and colors that bleed into diagonal squares. You can also add a bit of randomness to the roads using the same method to get potholes or grass tufts. Or you can use the patterns to make the road look like it is interacting with the things on top of and around it, to make it look more used near buildings, darker and more wet near water, and more grassy near a forest, etc. This may require a bit of fiddling and color hunting until you get the look you want.
4) Pick a starting location for the darkest color and put it in the center of the road to give it a worn down or wet road look. Do the opposite to make it look shiny, new and curved upwards.
5) Add a random end piece to your road so that it can vanish into the surrounding landscape.



can do this with more or less colors with different lengths of color variation and color contrast to have one color stand out more or less to get the look you want