In HTML, colors are specified by a six-digit hexidecimal code. Color tags are seperated into Red, Green, and Blue. The lowest numbers are darkest and the highest numbers are lightest. Thus, for a color that's solid red , you might use FF0000. That specifies "FF" (the highest value in 2-digit hexidecimal code) for red, and 00 each for green and blue. To get a medium Yellow you'd use 888800, which is equal parts red and green, and no blue. (88 is near the middle of the scale in 2-digit hexidecimal code). To get dark blue you'd probably use 000040, which is zero parts red and green, and a low-intensity blue. It's a bit complicated to explain colors in serious detail to a beginning designer. However, if you want, you can check out my virtual colorwheel or my color chart.