@ Fiorite- The phenomena you witnessed has everything to do with the wavelength of light. Sunlight emits all of the different wavelengths of visible light (as well as some invisible wavelengths) in a continuous spectrum. This is why rainbows are created (the raindrops act as prisms). Artificial light on the other hand only emits some wavelengths of light, depending on the elements used within the bulb. Since artificial light does not emit a full spectrum of light, it shows up as a line spectrum. the gaps between the lines are the wavelengths that the light source does not emit.
If you could somehow create a rainbow with artificial light, it would look like an arc of banded colors with gaps in between and missing colors. This is also why artificial light will sometimes cast a slight yellow, blue, or orange hue on things.