Cancer prevention tip #2 is ... embrace the power of the rainbow and diversity
That is, eat a wide range of fruits and veggies with a wide range of colors. Ad the brighter/deeper the color the better. By doing this your diet will naturally contain a range of phytochemicals. And to quote Wikipedia....
Phytochemicals are chemical compounds that occur naturally in plants, such as beta-carotene. The term is generally used to refer to those chemicals that may affect health, but are not yet established as essential nutrients. While there is abundant scientific and government support for recommending diets rich in fruits and vegetables, there is only limited evidence that health benefits are due to specific phytochemicals.
Thus, by eating a range of foods and colors, you cover your assets, by natural and delicious means.
I just bought some purple sweet potatoes, myself.