@mariusstrom From the legend in the corner I’d say yellow and red are flipped. At the same time, red would signal a warning. Since there are roads that have not been plowed at all, those would probably be more dangerous than the (then) red ones.
Coming at this with color blindness in mind, I wonder if multiple shades of the same hue would be more accessible. Make them all different shades of blue, with darker colors representing most recently plowed roads.