There are many flaws roasters and producers find in green beans. There can be various reasons behind those flaws. Good thing is all defects are identifiable so the more educated the roaster easier it is to avoid those defects and beware about them.
This article discusses green coffee bean flaws in general. The flaws can be categorized too in accordance with the factors that cause those certain kind of flaws in green beans like improper harvesting, irresponsible processing or bad storage etc but in this article we are mainly trying to discuss what physical appearance some of the flaws may have so they can be better identifiable.

Dull color
Dull beans can be a result of either over-drying or insufficient drying of the coffee bean. Either way the resulting roast they give is also dull which gives woody taste to the final cup of coffee. Such beans are typically whitish brown.
Usually such beans result because either they have been in storage for too long (more than two years) or they weren’t properly dried under proper sunshine. Not the right amount of sunshine and beans begin to mold from the inside. As a result, the beans do dry overtime but because of the inner fungal growth and not natural moisture loss.

Amber color
Amber beans typically exhibit shiny golden outlook. Usually this happens because of the deficient soil. Upon roasting they remain pale and flavor produced will be bitter.

These beans appear rather silvery. They possess a tacky, rough and whitish outer skin. This kind of beans is usually drought affected. Upon roasting it leaves behind too much residue giving the final cup a grassy or potato like flavor.

Machine damaged
When the coffee cherries are treated in the de-pulping machine, beans may get broken or chipped as a result final roast can be uneven.

Insect damaged
Such beans exhibit holes in them caused by pests like the coffee beetle borer or the white stem borer. Some beans also possess yellow to black spots which are the bruises given by Antestia bugs. Insect damaged beans tend to be sour, alkaline and earthy and resulting roast is soft.

Multiple centre cuts
This usually happens under a situation where nutrients are lacking like drought or deficient soil. Either way the result is distorted bean which can split during roasting. Beans are soft in this case and hence will get over-roasted giving the final cup a burnt flavor and heavy body.

As the name suggests such beans are rotten because of over-fermentation. They look rotten and carry a tobacco like color. These are enough to ruin a cup because of the rotten smell and sour taste they give off. Even slightly over fermented give off onion like flavors.

Common coffee plants diseases are coffee berry disease and leaf rust. The beans in such cases are poorly developed, dark colored ragged. Since coffee cherries are harvested and not the coffee beans, disease affected beans also get mixed with normal harvested beans.

Understanding the flaws is the step that can be taken towards avoiding them. Analyzing green beans is just one of many quality control measures that exist in specialty coffee sector.
The better the collaboration between producers and roasters higher are the chances to decrease the flaws. Another step is to understand specific conditions of each world region where coffee grows. Some areas could be drought affected while other might have received untimely rain and some other might be struggling with plant disease or other particular coffee pest. The point is better informed roaster can make better choices while purchasing green coffee.