I don't mean the images displayed on a panel; I mean the light from the panel if it were used to illuminate something else. Because you have only three narrow wavelengths of light, you lose 99% of the color information contained in the illuminated object's absorption spectrum.

Actual LED lamps work around this issue by using phosphors to broaden the spectrum.

This quality of light is measured by the Color Rendering Index; the phenomenon of color differences due to narrowband light sources is known as metamerism.

The images displayed on a panel do not suffer this issue, because our eyes can detect only 3 "dimensions" of color; hence 3 narrowband illuminants suffice. (And in fact narrowband is necessary for a broad color gamut.) It is only when reflection/absorption comes into play that metamerism matters.