Sunsets and sunrises are relatively easy to photograph because the exposure is not as critical as it is with some other scenes. If you underexpose the scene slightly, the colors will simply be a bit richer and darker. Slight overexposure will make the same scene slightly lighter.
The colors in the sky are often richest in the half hour before the sun rises and the half hour after it sets. It pays to be patient as you watch the sky change during these periods. For one thing, the sun itself is below the horizon and not in the image so exposure problems are greatly reduced. Also if there are clouds in the sky at those times they are more reflective of colors.
Also consider using a remote shutter switch and tripod since low light requires longer exposures, such as the moon or night scenes..Longer exposures should allow you to capture much more the exisitng colors.
There is an excellent book with CD, that I bought even though I have the SX50, which was written specifically for the SX40.
That's where I get a lot of my tips. Its called A Short Course on Powershot SX40HS Photography written by Dennis P. Curtin. It's very informative and is 161 pages long.
And of course you'll get great information here too.
