Ethiopia is the "birthplace" of coffee, with it's name supposedly originating from the Kaffa forests. Despite being one of the original places for coffee beans, the culture isn't well established enough or as advanced as some other countries and the bean quality varies tremendously from one location to another.
It's not uncommon to see uneven roast colours from even the best quality ethiopian coffees. Some regions dry process their coffees, some regions wash theirs, and the Sidamo region does both!
The Yirgacheffe and and Limu have a lighter body and less earthy and wild tastes in their cup compared to the dry processed varieties. Much like fresh produce, when harvested at the peak of the season the coffees are some of the best in the world.