In "wine speak", the palette consists of just white, red and rosé. Within each of these colours, though, there is a wide spectrum of shades that can tell the drinker a much deeper story about the wine he is drinking. When you examine a glass of wine, it is best to look at it against a white background (a piece of paper helps if the tablecloth isn't white). Examine the colour from the centre of the glass (this is called the core) to the rim (this part, which can vary from a lighter shade of the core colour to pale and watery, can tell you how intense or aged a wine is).
What's also important is the clarity of a wine. Is it clear? This could mean a wine has been filtered before it went into the bottle. Slightly cloudy? Could be a sign of age or that it was produced by a "natural" winemaker, one who prefers not to filter so as to have all the flavour components in the bottle for ageing. Cloudy? This is most likely an old bottle and one would need to decant it before drinking.
For white wines, which aren't really white but myriad shades ranging from straw, yellow and gold to amber, the more intense the colour, the older the wine could be.
a wine that is a pale straw colour, maybe with hints of green, is likely to be a young wine of a recent vintage (within one or two years), and probably a sauvignon blanc or chardonnay that's seen no oak. Generally speaking, these wines will have a watery (clear) rim, which is a sign of youthfulness. If the wine is a slightly more intense straw colour, it could be a riesling, pinot grigio/pinot gris, or a pouilly-fume (a sauvignon blanc that's been partially aged in gently used oak barrels).
a yellow-ish wine is usually a chardonnay that's seen a bit of oak. If there's a hint of green, it shows that it is probably a young wine (one to three years old). A more concentrated shade of yellow would be an indication that the wine has spent more time in oak, probably six months to a year.
could indicate two things. One, that the wine was barrel fermented and aged in oak - think of a rich buttery Californian chardonnay - this would be the usual method a winemaker would use to make this. And two, that it's sweet. Think of a sauternes or an ice wine, where the grapes are harvested quite late, therefore concentrating the juices and intensifying the colour.