Which type of bottle is least effective at preventing skunking?

Clear bottles are the least effective at preventing skunking because they provide no protection against UV light, which is a significant contributor to the chemical reaction that causes the skunky flavor and aroma in beer. When light, particularly UV light, interacts with certain compounds in the beer, such as hops, it can lead to the formation of 3-methyl-2-butene-1-thiol, the compound responsible for the "skunky" smell.

Dark-colored bottles, like brown or green, filter out a substantial amount of this harmful UV light, thus protecting the beer from skunking more effectively than clear bottles. Ceramic bottles can also provide good protection since they prevent light penetration altogether, but clear bottles offer no such advantage, making them the least suitable choice for preserving the integrity and quality of the beer.