Vodka, tequila, rum, and gin all have clear varieties. Of these liquors, most can take on color through processes like barrel aging that change them from clear liquors to brown ones.

When you see a spirit that's brown, it's because that liquor has spent time aging in the presence of wood — generally (and potentially exclusively) in the form of a barrel. Now, here's where it gets more detailed: the charred wood of a barrel imparts color and flavor to the spirit resting within.

White liquor is a strong alkaline solution composed of sodium hydroxide (NaOH) and sodium sulfide (Na2S) in a mixture of hot water. It is used in the first stage of the Kraft process in which lignin and hemicellulose are separated from the cellulose fiber in wood chips for the production of pulp.

Using this logic, a reasonable and objective definition of Light Spirits, consistent with the applicable legislation / regulations is: distilled alcoholic drinks with an ABV of at least 15% and not more than 26.25%.