
Tequila añejo is blue-agave tequila aged at least a year in oak (usually ex-bourbon casks of 600 L or less), which turns it amber, softens the agave and layers on oak, vanilla and caramel. It’s the deep-aged rung above reposado; three years or more makes it extra añejo.
Long oak over agave is the shape, and less oak is the usual compromise: reposado is the nearest swap, and a blanco is the swap that gives it up entirely. A barspoon of an aged rum or a soft cognac puts a little of the barrel weight back without adding sugar.
Reposado rests two to twelve months against añejo’s minimum of twelve, and the cask rule differs too: the size limit in the definition above binds añejo only, so a reposado may rest in a vessel of any size. The extra time shows in añejo as more vanilla, more color and less raw agave.
Blanco is unaged and clear, all raw agave; añejo is the same spirit after a year or more in oak. Blanco keeps a drink bright and green, añejo gives it vanilla, color and weight.
"gold tequila = aged"
Gold ("oro") is often a caramel-colored mixto, not aged tequila at all.