Wash all of the green grapes after detaching them from stems. Place in a bowl, that will accommodate the remaining ingredients.
Detach the black grapes from the stems and wash those as well. Place on a surface. Cut each in half. Using a paper clip, that has been bent straight, pull out the seeds from each half, using the smallest eye, place each cleaned half in the grape bowl, making sure there are no seeds still attatched.
Add the grated lemon zest, sugar and strain over the orange juice.
Stir well and cover, chilling two or three hours before consumption.