Updated: Sep 16, 2020
Decanting wine serves two purpose 1- it enables the wine to be poured off any sediment, deposit in the bottle. 2- it aerates the wine sometimes helping young , stiff ,hard wine to show itself to advantage. If you are serving a red wine while it is still really young to be at its best then decanting will bring it on. Decanting wine looks well on a dining table and it is fair to say that an old wine deserve decanting and young wine needs it. Any body can test and see how decanting wine opens the wine for example take two same bottle of wine decant one get it aerated and serve other bottle directly without decanting and then compare.
How much time you should give a wine in the decanter? depends entirely on the wine, old wine should never be over aired but if you are serving delicate wine then you simply pour them from the bottle.
Wine colour can say a lot about its ages and the easiest way of examining the colour of a wine is to tilt the glass so that the bowl is at the angle of 45 degree away from the body. Hold the glass over white napkins , paper and look down on the wine rather than up at it. Young white wines can be very pale in colour and they generally tend to be paler. Mostly young white wine starts from slight tinge of green colour when they are young and as they age they go from very pale yellow colour then it begins to turn silvery gold and when they are aged well they turn marigold in colour.
Many red wine also deepen and intensify in colour as they develop in bottle and when they reach there prime the edge of the wine may begin to assume a beautiful tawny colour which gradually spreads throughout the rest of the wine