Colored text can be very effective on your web-site, but you need to be aware of some of the “gotchas” of text colors.
When you select a design using the Design Chooser in your control panel, you're selecting the default text color as well. Light text on a dark background will select a pleasing contrast, as will dark text on a light background. But if you manually change the color of the text on any of your pages (using the color picker in the mini-word processor built into each page layout) you can cause your text to be unreadable. For example, if you're using dark text on a light background and select some text that you want to stand out by changing the color to red, be aware that the text will be red even if you subsequently change the design to light text on dark background. In that case, the red text may be almost invisible on a dark background.
Unless it's absolutely necessary, let the Design Chooser pick the colors for your text – it'll make things easier for you to change in the future!