Yes you can but if doing a one-step process (where both powders are combined without dye release of henna first), you will still get shades of brown in line with proportions below (remember the more percentage of henna the lighter the colour towards light browns and the more percentage of indigo the darker the colour towards dark browns and black):70% henna and 30% indigo - Light brown70% indigo and 30% henna - Dark brown50% henna 50% indigo - Medium brown90% indigo 10% henna - Nearly Black (very dark brown)