Color is pretty good for separating things. That’s what your basic pie chart is, isn’t it? You tell the slices apart by color. With enough color contrast, you might be OK, but you might be even better off (particularly where accessibility is concerned) using patterns, or a combination.
Patrick Dillon tackled the Pie Chart thing
Enhancing Charts With SVG Patterns:
When one of the slices is filled with something more than color, it’s easier to figure out [who the …
Simple Patterns for Separation (Better Than Color Alone) is a post from CSS-Tricks