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2.2 CSS Background

The CSS background properties are used to add background effects for elements.

CSS background-color

The background-color property specifies the background color of an element.

Example 1: CSS background-color

The background color of a page is set like this:

body {
background-color: lightblue;
}

With CSS, a color is most often specified by:

• a valid color name - like "red"
• a HEX value - like "#ff0000"
• an RGB value - like "rgb(255,0,0)"

Look at CSS Color Values for a complete list of possible color values.

Other Elements

You can set the background color for any HTML elements:

Example 2: CSS background-color example!

Here, the <h1>, <p> and <div> elements will have different background colors:

h1 {
  background-color: green;
}

div {
  background-color: lightblue;
}

p {
  background-color: yellow;
}

Opacity / Transparency

The opacity property specifies the opacity/transparency of an element. It can take a value from 0.0 - 1.0. The lower value, the more transparent:

• opacity 1
• opacity 0.6
• opacity 0.3
• opacity 0.1

Example 2: Transparent Boxes part 1

div {
  background-color: green;
  opacity: 0.3;
}

Note: When using the opacity property to add transparency to the background of an element, all of its child elements inherit the same transparency. This can make the text inside a fully transparent element hard to read.

Transparency using RGBA

If you do not want to apply opacity to child elements, like in our example above, use RGBA color values. The following example sets the opacity for the background color and not the text:

• 100% opacity
• 60% opacity
• 30% opacity
• 10% opacity

You learned from our CSS Colors Chapter, that you can use RGB as a color value. In addition to RGB, you can use an RGB color value with an alpha channel (RGBA) - which specifies the opacity for a color. An RGBA color value is specified with: rgba(red, green, blue, alpha). The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).

Tip: You will learn more about RGBA Colors in our CSS Colors Chapter.

Example 3: Transparent Boxes part 2 Using RGBA

div {
  background: rgba(0, 128, 0, 0.3);
 /* Green background with 30% opacity */
}