Color

One of you had mentioned wanting to learn more about color balance.  Here is a chart explaining color temperatures of "white" light sources as shown on a Kelvin scale.  As you can see the color shifts from warm (candle) to cool (daylight).  When shooting with film, photographers must take these levels into account by using the right film (tungsten, type A or daylight) or filter.  Digital photographers can either set the color balance in their camera or adjust afterwards in an editing program like photoshop.

Here you can see the effect that the sun's proximity to the horizon has on color.

The first and last hour of the day are known as the "golden hour," because of the overall warmth the quality of light adds to color photographs.

Okay, this doesn't really have much to do with color but I thought you might find it interesting... This photograph by Richard Misrach was made using two exposures - one with existing light (the background mostly) and the other with a flash (the highlight of the plant).  First he probably made a longer exposure with the light existing at dusk after the sun had gone down but while there was still a glow in the sky.  Then he shot the plant in the foreground with a flash exposure.  If he had exposed just for the sky, the plant would have been a silhouette against the sky.  If he had exposed just with flash, the sky would have been black.  The combined exposure records the scene in a way only possible with the help of a camera.  Interesting, no?