It's mixed. The issue really is in that the testers aren't 'darker' people, though it's not really their fault either.
In color film photography they chose the CYM spectral sensitivities to best represent US white women in heavy make-up under stage lights. It was the 1920/30s afterall. The spectral sensitivities haven't changed much since then as a result (an example of the Lock-In effect in full swing). CCD and CMOS camera dopants are chosen to represent the spectral sensitivities that are similar to film, though physics does come charging in on those.
To be honest, yes, it's hard to photograph darker skinned people without sufficient full-spectrum light. Darker skin absorbs more radiation at the solar-peak frequency (~550nm, the light green of most plants), as the melanin is evolved to do. That said, if your film/sensor can see far outside of the solar peak, then you'll pick up darker skinned people better. Old-timey tin-type photographs could see well into the UV (notice how there never are any clouds in pictures taken way back when) and darker skinned people showed up just fine in those old photographs as a result.
Fun-Fact: the front facing camera on most mobile-phones does not have and IR filter on it, specifically to help with these issues of darker skin. Next time you are near a handle-less toilet with an IR sensor, you can use the front facing camera to see the little IR LEDs beeping to see if you are there. You can also use the front-facing camera to see security lights and what not, typically those are IR ones too.
UV light could also be used, but it is more damaging over time, and thus lower frequency IR light is preferred.