I too used the granny smith apples someone else recommended, but next time might try an apple with a pinkish skin just for the contrast as the kohlrabi has a slight green tinge to it too. (epicurious.com)
They have gorgeous blue flight feathers and a lighter green tinge on the underside of their tails. (thesprucepets.com)
Certain herbals medicines or supplements may also cause your milk to become green tinged. (expressing-mama.com)