Regarding colors, remember that a little goes a long way.
Although I am certainly no color expert, here are my thoughts on the subject based on what I have seen and learned...
(I am hoping that others will chime in here with their thoughts and opinions, also.)
1. Do not feel like you have to color in everything. Look for where a little more color makes the page more appealing. Start off with adding a little bit and adjust it as you go, like seasoning a good meal. Also remember, that color can come from a variety of sources, even the photos on a page.
2. Avoid really intense colors. Frequently, colors can be like spices added to food. You can have too much (or too little) or the wrong combinations. Also, some people will like more "spices" (more color) or a different combination of "spices" (colors). It is important keep in mind that people's perception of color is very subjective and varies, so if you ask for feedback on your colors, get it from *several* people, but do not necessarily expect a consensus.
3. I find that color *contrasts* are frequently what makes a page appealing. In other words, the colors in one part of a page relative to the rest of the page. In my view, anything containing color, such as photos/images on the page can contribute or detract from this. If you have a lot of colorful photos on a page, then you may consider those to be "the color" and just leave the background white for a good color contrast.
4. If you are uncertain as to what colors to work with, then refer to the colors in your selected banner and use different shades of those colors as your "color theme". Most of the banners are created with three or four basic color hues. A "hue" is the base color from the color spectrum. For example, yellow, blue, green, etc. However, even though you may have three color hues to work with when using this approach, remember that there are an infinite number of shades/intensities of those colors you can work with. These theme colors are pre-loaded in the palette of the color pickers for those who wish to use this approach.
5. How to use the color pickers: You can adjust the color hue but clicking and dragging the slider handle up and down in the color hue slider on the right side. You can adjust the color intensity by just clicking and dragging the dot around in the color gradient square to find the intensity that you like.