Colour is a key indicator. Check the wine against a white background. Tilt the glass away from you and observe the body of the wine as well as the rim. It is easier to pick out the type of colour looking through this thinner film of wine than trying to look through the body of it. For red wines the rim of the wine should be closely observed.
Colours range from light ruby red to black.
Browning indicates oxidation or a lot of age. This is common to both white and red wines. Note that natural light is best, fluorescent light will make most reds appear brown. Let's not forget Pink wines, Roses or Blush wines cover a spectrum from light salmon pink to good ruby colour. Legs, Church windows or tears all refer to the post swirling syndrome.