For Red, Green, and Blue, it takes values from 0 to 255, and then converts these values to a hexadecimal string that can be used to specify colors in the html / css code. Photo editing software usually represents color in RGB, so if you want to use the colors you use in the photo editing software as the background of your html, you need to get the hexadecimal representation of the RGB values. This tool allows you to retrieve these values.
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