Off-color or darkened fries are typically a result of potatoes not properly stored and in fact, stored too cold. When held below 41°F for too long, the starches in potatoes (any source) convert to sugar, and this negatively affects the cooking performance. There are ways to test for high sugars as well as guidelines for proper potato storage. (Both attached). Potatoes always appear rugged and indestructible, but they actually require tender, loving care in order to perform at their best.