The coffee: Ethiopian single origin natural processed.

The concern: there are a significant amount of light colored beans in this batch of coffee. This has me concerned about the quality of the beans and/or the roast itself, and frankly, I'd rather toss the bag than have a sub-par coffee experience. The shots I've pulled so far have been sour, but I can't blame that solely on the beans. I haven't dialed it in completely yet.

The question: is it normal for natural processed beans to have a high amount of lighter colored beans or not? If not, then I'm guessing these are quakers or flaws in the roasting process signaling a low quality batch of coffee in this bag.

The lighter beans could be "Quakers" that can occur with natural processed coffee, and are there because they were not screened by the roaster. If there are more than a few it's a subgrade roast. If there is an overall variation in color then the roaster did a crappy job (this is an SO, not a medley or some other blend). I agree that brewing including them would add under extracted tastes and make it impossible to dial in well.

You don't get Quakers in washed coffees because they float and are very easy to separate using a wet process. It's harder to screen in green coffee these immature beans, but easy once roasted because they don't color. They taste a bit like peanut butter if you eat them, and won't ruin the roast but you can cull them if you like.