Peel and grate the cucumber, then wrap it in a clean dish towel and squeeze the juice into a dish. Discard the pulp. Peel and grate the onion, then wrap it in a clean dish towel and squeeze the juice into a dish. Discard the pulp. If preferred, use a juicer.
Combine three tablespoons of the cucumber juice, one tablespoon of the onion juice, cream cheese, salt, pepper, and food coloring in a bowl. Mix with a fork or mixer until well blended.