css11 CSS RGB Colors
https://www.w3schools.com/css/css_colors_rgb.asp
An RGB color value represents RED, GREEN, and BLUE light sources.
RGB Value
In CSS, a color can be specified as an RGB value, using this formula:
rgb(red, green, blue)
Each parameter (red, green, and blue) defines the intensity of the color between 0 and 255.
For example, rgb(255, 0, 0) is displayed as red, because red is set to its highest value (255) and the others are set to 0.
To display black, set all color parameters to 0, like this: rgb(0, 0, 0).
To display white, set all color parameters to 255, like this: rgb(255, 255, 255).
Experiment by mixing the RGB values below:
<!DOCTYPE html> <html> <body> <h1>Specify colors using RGB values</h1> <h2 style="background-color:rgb(255, 0, 0);">rgb(255, 0, 0)</h2> <h2 style="background-color:rgb(0, 0, 255);">rgb(0, 0, 255)</h2> <h2 style="background-color:rgb(60, 179, 113);">rgb(60, 179, 113)</h2> <h2 style="background-color:rgb(238, 130, 238);">rgb(238, 130, 238)</h2> <h2 style="background-color:rgb(255, 165, 0);">rgb(255, 165, 0)</h2> <h2 style="background-color:rgb(106, 90, 205);">rgb(106, 90, 205)</h2> </body> </html>
Example
Shades of gray are often defined using equal values for all the 3 light sources:
Example
<!DOCTYPE html> <html> <body> <h1>Shades of gray</h1> <p>By using equal values for red, green, and blue, you will get different shades of gray:</p> <h2 style="background-color:rgb(60, 60, 60);">rgb(60, 60, 60)</h2> <h2 style="background-color:rgb(90, 90, 90);">rgb(90, 90, 90)</h2> <h2 style="background-color:rgb(120, 120, 120);">rgb(120, 120, 120)</h2> <h2 style="background-color:rgb(180, 180, 180);">rgb(180, 180, 180)</h2> <h2 style="background-color:rgb(210, 210, 210);">rgb(210, 210, 210)</h2> <h2 style="background-color:rgb(240, 240, 240);">rgb(240, 240, 240)</h2> </body> </html>
RGBA Value
RGBA color values are an extension of RGB color values with an alpha channel - 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 (not transparent at all):
Experiment by mixing the RGBA values below:
Example
<!DOCTYPE html> <html> <body> <h1>Make transparent colors with RGBA</h1> <h2 style="background-color:rgba(255, 99, 71, 0);">rgba(255, 99, 71, 0)</h2> <h2 style="background-color:rgba(255, 99, 71, 0.2);">rgba(255, 99, 71, 0.2)</h2> <h2 style="background-color:rgba(255, 99, 71, 0.4);">rgba(255, 99, 71, 0.4)</h2> <h2 style="background-color:rgba(255, 99, 71, 0.6);">rgba(255, 99, 71, 0.6)</h2> <h2 style="background-color:rgba(255, 99, 71, 0.8);">rgba(255, 99, 71, 0.8)</h2> <h2 style="background-color:rgba(255, 99, 71, 1);">rgba(255, 99, 71, 1)</h2> </body> </html>
标签：color,rgb,RGB,values,rgba,Colors,CSS,255 From： https://www.cnblogs.com/emanlee/p/18221250