Pour three tequilas side by side and the colour changes from clear to pale straw to deep amber. The agave and the still are the same. What changes is time spent in an oak barrel, and Mexican law puts a name on each stage: blanco, reposado, añejo and extra añejo. Drag the slider to see what each stage means.
Fresh tequila is clear and tastes of cooked agave: sweet, vegetal, a bit peppery. Oak adds three things. It lends flavour compounds, mostly vanilla, caramel and spice. It lets a tiny amount of air in, which softens harsh edges. And it gives colour. Small barrels expose more liquid to wood, so the same time in a small barrel changes the spirit more than in a big one.
That is why the rules cap barrel size for añejo and extra añejo at 600 litres. A tequila can also be a young spirit in a tiny cask or an old spirit in a huge one; the label class only tells you the minimum time.
Blanco is unaged or rested under two months. Reposado means "rested": at least two months in oak. Añejo means "aged": at least one year. Extra añejo is three years or more, a class added in 2006.
You may also see joven, which is usually a blanco blended with aged tequila, and cristalino, an aged tequila filtered to remove colour. A cristalino still carries its underlying class on the label.
Darker does not mean better, and it does not always mean older. Colour can be adjusted, so read the class on the label.
Separate from ageing is what the tequila is made from. Tequila labelled 100% agave gets all its sugar from blue agave. Plain "tequila" (called mixto) needs at least 51% agave sugars, with the rest from other sugars. If you want to taste the plant, look for 100% agave on the label, whatever the age.
As a rule of thumb, match the bottle to how much it has to say in the glass. A Margarita is lime, orange liqueur and salt, and a blanco keeps the agave bright. A reposado works if you like a rounder, slightly oaky Margarita. Añejo and extra añejo belong in a small glass, with a splash of water if you like. Their wood and caramel notes fight the citrus in a sour.
The rule breaks easily. Plenty of people love a reposado in a Paloma, and an añejo makes a fine stirred drink, such as a tequila Old Fashioned. Try a pair side by side and decide for yourself.
If you want the flavour without the strength, a Paloma made with a splash of tequila topped up with grapefruit soda and plenty of ice is a lighter long drink. Or skip the spirit and use the same grapefruit, lime and salt with soda water. Either way, drink responsibly, and never drive after drinking.