Put two valid CSS color values, in the format you choose--hex, RGB, RGB%--then choose the number of midpoints you'd like between them and blend. You'll get intermediate colors with their hexadecimal codes.
This section of the cloford.com website provides a web-safe diagram, web-smart colours, named colours, 500+ colours, web-safe colours by hue, and colour links.
Elements of Design: Color
Of all the design elements, color has the most immediate and profound effect on visual perception.
The color of an object is determined by what happens when a surface is hit by light waves.
Of all the design elements, color has the most immediate and profound effect on visual perception.