Wash grapes. Place grapes on a clean towel and roll grapes in towel to dry.
Place grapes in a bowl. Squeeze lime half over grapes and mix with your hands to combine. Place half of grapes in a pint-sized zip-top plastic bag.
Place mango in mini-food processor. Process until fruit is a powder.
Sprinkle half of mango powder over grapes in plastic bag. Close bag and shake to combine. Pour grapes into a dry bowl. Repeat with remaining grapes and mango powder.