Usually the color of the fruit or veggies determines that group it fits in, however there are some that don't quite fit that mold.
The Nature's Prescription book outlines specific foods.
In general, you can search the categories.
Anti-inflammatory = yellow/orange (turmeric, ginger, etc.)
Immune boosting = orange (orange, carrot, papaya)
Purple = high in antioxidants and brain boosters (blueberries)
Red = anti-aging and heart health (strawberries, cherries, etc.)
Green = cleansing (lettuce, kale, spinach, broccoli, etc.)