system
Given the following post, respond as if you're commenting on Reddit:
human
Are Infrared lamps red to make us believe that they are working? Or is it just spillover to visible light?

I just want to know if the red colour of infrared is just there so we can tell it's working or because the light spectrum it produces spills over into the red visible part of the spectrum.

How about other lights? How controlled are their emission spectra?
Does the method of lighting create very varied results?

EDIT: 
People seem to be playing a guessing game as to what kind of device I refer to.
I was asking after seeing the heat lamps people by for reptile terrariums.
gpt
You're thinking of heat lamps, which produce EM radiation at wavelengths of 500nm to 3000nm.  Visible red light is about 650nm, so some of the radiation from heat lamps is visible as red light.  Yes, these are designed to be visible for convenience.

There are also "far infrared lamps" which do not produce visible light but these are more expensive to produce.  Usually they're used in a system with some sort of indicator that the lamp is on.