Oh sure--Those are the ones we call 'grow lights'. They contain: 1. the full daylight spectrum, 2. elevated red zone at about 3000k, 3. elevated blue zone at about 5000k. Most grow lights utilize a tri, (meaning 3) phosphor system to achieve that. The human eye cannot readily detect this extra red and. blue when a full spectrum of light is incorperated; although if one knows it's present, you'll will be able to detect it a little. LED grow lights, on the other hand, are generally very wavelength specific, so most of those you'll see appear (Edit) only red and blue. Edit; this should read: red or blue or some combination of both, red and blue diodes.
Now, you mention you saw a double tube set up that has a 4000k tube as well. That's interesting because I was going to talk about that earlier, but backed off from it because I felt it would just add more confusion because in photobiology, we first have to learn the most phosyhthetically active regions (PAR) of plants are the regions of red and blue wavelengths. So we sort of concentrated on red and blue for a while. But there is another zone: the 'green zone'. It lies right between the reds and blues at about 4000k. It is sometimes called 'moonlight'. Many people use it as a nightime period lightsource on plants. Many people believe there may be a whole lot more going on with plant functions at night than we currently realize and that green light is benificial to those functions. But I don't have any green tubes and I don't use any type of nightime period lighting. It's and interesting area to me tho, and I'm still learning more about it's use every day. So far it's only made in as a single zone, separate tube as far as I know. The current grow lights don't have that elevated green zone but do have some green.
My double tube setup I have that you mentioned---I only use doubles when I need a broader spread at the same intensity such as when I have two or three rows of pots or baggies, etc.
