In CSS, you can use the background-color attribute to set the background color, the syntax is "background-color: color value;". Color values can be defined using color names, hexadecimal values, RGB or RGBA values, HSL or HSLA values.

The operating environment of this tutorial: Windows 7 system, CSS3&&HTML5 version, Dell G3 computer.

css sets the background color

The background-color property sets the background color of the element.

The background-color property sets a solid color for the element. This color fills the element's content, padding, and border areas, extending to the outer bounds of the element's border (but not the margins). If the border has transparent parts (such as a dotted border), the background color will show through these transparent parts.

Example:

   
  
这是标题 1
 
这是标题 2
 
这是段落
 
这个段落设置了内边距。
  

Rendering:

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How to write css color values:

1. Use the color name

Although currently There are about 184 named colors, but there are only 16 color names that are actually supported by various browsers and recommended as CSS specifications, as shown in the table below.

Table 1: Color names recommended by CSS specifications

/*名 称 颜 色 名 称 颜 色 名 称 颜 色 black 纯黑 silver 浅灰 navy 深蓝 blue 浅蓝 green 深绿 lime 浅绿 teal 靛青 aqua 天蓝 maroon 深红 red 大红 purple 深紫 fuchsia 品红 olive 褐黄 yellow 明黄 gray 深灰 white 壳白*/

It is not recommended to use color names in web pages, especially large-scale use, to avoid that some color names are not parsed by the browser, or are different Differences in how browsers interpret colors.

2. Hexadecimal color

Hexadecimal symbols #RRGGBB and #RGB (such as #ff0000). "#" followed by 6 or 3 hexadecimal characters (0-9, A-F).

This is the most commonly used color selection method, for example:

#f03 #F03 #ff0033 #FF0033

3, RGB, red-green-blue (RGB)

The color value is specified as the color of the rgb code. The function format is rgb(R,G,B), and the value can be an integer or percentage from 0-255.

rgb(255,0,51) rgb(255, 0, 51) rgb(100%,0%,20%) rgb(100%, 0%, 20%)

Extensions: RGBA, Red-Green-Blue-Alpha (RGBa)

RGBA extends the RGB color mode to include an alpha channel, allowing the transparency of a color to be set. a represents transparency: 0=transparent; 1=opaque.

rgba(255,0,0,0.1) /* 10% 不透明 */ rgba(255,0,0,0.4) /* 40% 不透明 */ rgba(255,0,0,0.7) /* 70% 不透明 */ rgba(255,0,0, 1) /* 不透明，即红色 */

4. HSL, hue-saturation-lightness (Hue-saturation-lightness)

Hue (Hue) represents the color circle (that is, a circle representing a rainbow) ring) at an angle.
Saturation and brightness are expressed as percentages.
100% is full saturation, while 0% is a grayscale.
100% lightness is white, 0% lightness is black, and 50% lightness is "normal".

hsl(120,100%,25%) /* 深绿色 */ hsl(120,100%,50%) /* 绿色 */ hsl(120,100%,75%) /* 浅绿色 */

Extension: HSLA, Hue-Saturation-Lightness-Alpha (HSLa)

HSLa extends from the HSL color mode and includes the alpha channel, which can specify the transparency of a color. a represents transparency: 0=transparent; 1=opaque.

hsla(240,100%,50%,0.05) /* 5% 不透明 */ hsla(240,100%,50%, 0.4) /* 40% 不透明 */ hsla(240,100%,50%, 0.7) /* 70% 不透明 */ hsla(240,100%,50%, 1) /* 完全不透明 */

5, transparent

Special color value, indicating transparent color. Can be used directly as color.

For example: color:transparent Set the font color to transparent

  
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