This site will help you select colors for a web page. Select a color for the background and another one for the font and click "Apply Colors".

You can use one of the 140 predefined html colors, eg "pink", "slateblue". Select them from the dropdown box. (See Named Web Colors for a complete list.) Or you can select "RGB hexadecimal" or "RGB decimal". Then you will be prompted to enter the values for Red, Green and Blue. If you selected "decimal" you will enter a number between 0 and 255 for each color. If you selected hexadecimal you will enter a number between 00 and ff.

For more information on how colors are rendered on the internet, read the w3schools introduction to web colors: RGB Web Colors.