RGB and CMYK are different color models: RGB is additive and it's used on screens, while CMYK is subtractive and it's used on prints. RGB uses white as a combination of all primary colors and black as the absence of light. CMYK, conversely, uses white as the natural color of the print background and black as a combination of colored inks.

Every color can be represented by a combination of different values with different meanings.

Every color is slightly different, here is a list of the most similar colors and paints that have a name

Use one of these values interchangeably for any CSS property that accept a color as a value: color, background-color, border-color.

A tint is a mixture of a color with white, this will increase lightness. A shade is a mixture with black and this increases darkness. A tone is a mixture of a color with gray, it's used to control saturation.