I'm not particularly talented at choosing colors, so I'm always asking for advice when I make designs from people with a good sense.
But I've found a pretty good hack for webpages. You can see the result at my website, http://jimdavies.org/
Here's what you do: find the dominant picture on your webpage, and find its URL (right click and select "view image"). In the case of my webpage, it's this:
Then go to a website like the color palette generator and input your image.
It will tell you the dominant colors in the image. It will tell you the color identifiers for websites. Then you can change your website html...
Assuming the palette in the photo is good, the website's colors will be good too. And even if the photo has bad colors, at least your webpage will match.