Be sensitive to what sort of information the individual needs.
Always ask how they think of colors, as they will know how it's best described to them. Chances are they're used to being blind and know best how to deal with such things.
Make use of the senses that the person still has.
Many blind people are not blind from birth, and may simply need a reminder. For example, green is the color of grass, the leaves of trees, and seaweed; the person can smell and touch these things. Red is the color of blood and roses and hot chilis, etc.
Make use of the symbolism of color if the blind person is interested.
Bright greens represent growth and healing, blues tend to be calming and intellectual, red is very passionate and can mean anger or desire, and so on.
Describe what the color might mean to that person.
This is particularly useful for the shades of color. Use words the person can relate to, like soft, light, or cheerful for yellow.
Describe how the colors make you feel.
Gloomy greys might make you feel bored and sad, and cheery yellows and oranges might make you smile.
If the person is interested, tell them how when you mix two colors together it creates another color.
(For example, if you mix red and yellow, it creates orange.) Telling them this helps them connect these colors within their mind.