Distinctive variegated mophead flowers range from deep indigo-blue to magenta-pink. The long-lasting blooms age to an attractive green as they age. Like other Cityline hydrangeas, Mars is a dwarf plant that does not need pruning to stay nice and compact. Use it as a foundation plant, or as a show-stopping specimen in a container garden. The glossy green foliage is very mildew-resistant. Flower color is affected by pH. For blue flowers, the soil must be more acidic and for pink flowers the soil must be more alkaline. Add aluminum sulfate to the soil to encourage blue flower color.