RGB is a system for adding colors of light. This is always at odds with printed work that relies on blocking colors of light from reflecting off a page, as pages generally do not produce their own light.

RGB focuses on three specific wavelengths of light closely corresponding to the three colors most peoples' eyes are most sensitive to. Pantone relies on fourteen base pigments, and attempts to match along the entire spectrum of color.

Meanwhile, Pantone focuses on getting consistent color. A bottle of a certain ink bought decades ago should match with a package of dye purchased in the present day. Even if the pigments are produced using different chemicals, they attempt to match with each other under similar lighting conditions.

Something we take for granted with RGB is that results vary between different devices. The red color chosen by one manufacturer may differ from the red used by another. There can be variation within the model line of a certain device. The same device may show the same color values differently under different conditions (e.g. full daylight vs lights out, blue light filter, new vs old monitor).

Even #000000 black, which every device treats as the absence of light, may not match between different devices. Typical monitors will deflect as much light as they can, but cannot fully prevent a backlight from showing to some degree. Some newer monitors stop generating light, and so produce a darker black.