Color Composition and HTML

Possible Colors

The HTML specification requires browsers to be able to recognize the following 16 names of colors: black, green, silver, lime, gray, olive, white, yellow, maroon, navy, red, blue, purple, teal, fuchsia, and aqua.

This means that if you want the above cell to have a color of navy and a background color of fuchsia, you would type the following in the style sheet:

td#td1 {color: navy; background-color: Fuchsia }

Browsers can actually recognize more than these 16 names. However, if you design web pages by hand, you may not be able to remember more than these 16 colors. The next section shows you how to solve this problem.

Composition of Color

There are three fundamental colors. You know many colors, but each of the colors you know is made up of a combination of one or two or three of these fundamental colors. These three fundamental colors are red, green and blue.

HTML gives you 256 intensities (levels) of each of these three fundamental colors. The intensities are identified by the numbers 0 to 255 (not 1 to 256). This means that the red color can have any number from 0 to 255 (e.g. 0, 1, 2, 200, up to 255). This is also true for the green and blue colors. With this, the navy color is written as rgb(0,0,128), where rgb stands for red, green, and blue; the first number is for red intensity, the second number stands for green intensity, and the last number is for blue intensity. The three numbers are separated by commas in the expression. The fuchsia color is written as rgb(255,0,255). So the above line of code can be written as

td#td1 {color: rgb(0,0,128); background-color: rgb(255,0,255)}

where navy has been replaced by rgb(0,0,128) and fuchsia has been replaced by rgb(255,0,255).

The black color does not exist. You may be surprised to hear this, but it is true. The sensation of black is the absence of all three fundamental colors. This means that if you perceive a black color on an area of the screen, no color is actually emitted from that area of the screen. On the other hand, in HTML, white is a combination of the three fundamental colors, each at its maximum intensity. So the color black is written as rgb(0,0,0) and the color white is written as rgb(255,255,255).

The following table gives the Red-Green-Blue combination of the 16 colors mentioned above.

So instead of typing any of the above names in your CSS, you can type the equivalent RGB code. For example, instead of typing “purple,” you can type “rgb(128,0,128)”.