CSS RGB and RGBA Colors - W3Schools
https://www.w3schools.com/Css/css_colors_rgb.asp
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).
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