Some helpful info to help you differentiate buckwheat in its different forms if you are planning on using buckwheat in your cooking.
What buckwheat looks like after its harvested. It has a triangular-shaped shell. At this stage, the groats are still in their hulls, which have turned a dark brown or almost black color. Unhulled buckwheat can be grounded into flour and will produce a dark grayish colored flour with bits of black which is the hull.
After the hull is removed. Hulled buckwheat is called buckwheat groats and can come in light brown or pale green color. The buckwheat groats can be grounded up to become buckwheat grits which is used to make breakfast cereal. The hulls itself can be used as stuffing in making buckwheat pillows.
After the hulled raw groats has been roasted. Is it also known as Kasha. It is frequently used in cooking and can be grounded into buckwheat flour. Unlike the grounded flour from unhulled buckwheat, the color of the flour will be lighter.