What does the "a" in rgba mean? CSS RGBA Color Guide

RGBA is a CSS color that can set color value and transparency

Below is the use of rgba() to set the white color to 50% transparency.

p {
color: rgba(255, 255, 255, 0.5);
}

RGBA is an extension of the RGB color model. This acronym stands for the initials of the three primary colors red, green and blue, and the Alpha value represents the transparency/opacity of the color.

RGBA Syntax

The format of RGBA color representation is:

rgba(red, green, blue, alpha)

The first three values ​​(red, green, and blue) range from 0 to 255 as integers or from 0% to 100% as percentages. These values ​​describe the amounts of the three primary colors red, green and blue that are present in the intended color.
If you want to set pure red, set the red parameter to 255, and set green and blue to 0.

background-color: rgba(255, 0, 0, 1);

result:

Percentages can also be used:

background-color: rgba(100%, 0%, 0%, 1);

result:

The fourth value, alpha, specifies the transparency/opacity of the color and ranges from 0.0 to 1.0.

The following example sets the yellow color to 50% transparency:

color: rgba(255, 242, 0, 0.5);

CSS translucency is compatible with Firefox, IE, and Chrome, and the current browser versions are relatively high. You can use it in your project with confidence.