How a wine looks can tell you a lot. The colour of the wine can narrow down grapes, the "legs" indicate full bodied wines and hint at alcohol content and the rim of the glass can tell you the age of the wine and if it is mature enough to drink. So important is the sight of a wine, that I have seen Sommeliers get colour wrong, in a blindfolded tasting.
I once spent some time with one of France's top Sommeliers, who took part in competitions that used black goblets. His encyclopedic knowledge, helped me to catalogue a Cellar I was running at the time. He told me that being denied this bodily sense, really made him earn the prize money.
It has to be said that sight and smell are interchangeable in order, most people do it concurrently. When you are swirling the wine in the glass to unlock the smell, you can also look out for the other elements listed.
Legs are the thin residue of wine that trickle down the glass; thin and fast legs are more watery, thick legs and slow legs, show higher alcohol content. Higher alcohol content, for some people, equates to better wine. This is not always the case. It is, however, more information that you have deduced on the wine. Next week, sight continues with "Fifty shades of red".