Pour 1/4-cup hot water in a bowl, and add 1/4-cup cornstarch. Use a whisk to mix and dissolve the cornstarch in the water.
Pour two packets of powdered drink mix, such as Kool-Aid, into the cornstarch and hot water. Stir vigorously to eliminate clumps. Use any color of drink mix, or combine different colors.
If you don't have cornstarch or powdered drink mix, use turmeric. Pour powdered turmeric into a shallow dish, and wet a cotton ball or cotton swab with water. Stir the cotton ball or cotton swab around in the turmeric until it turns yellow. As needed, dip the cotton ball or swab in more water.
These henna substitutes work well for henna tattoos. Clean the skin thoroughly prior to applying the henna replacement. Use a loofah sponge to exfoliate and remove dead skin. Soak up the henna replacement with a cotton swab or fine-tipped paint brush, and apply to the skin to create the desired tattoo pattern.