Oddly enough, we are required to provide light for indoor panels (110.26D), but nothing is said about outdoor locations- which sometimes get dark :-).
Even so, nothing is said about what is enough light, or the quality of the light. As Trumpy has observed, you often end up blocking any light that there is- and customers / archetects seem to delight in placing panels in the darkest corners possible!
(At least they can't put them in the clothes closets anymore!)
Lighting is a realtive matter; in general, I would say that it ought to met the folowing criteria:
-Be similar to the lighting in the vicinity (so your eyes aren't forced to continualyy adjust);
-Be at least bright enough to read a newspaper by;
-Be somewhat diffuse or indirect, as from a fluorescent strip light; and,
-Be essentially white, so that color perception is not affected.
Now that's all fine, but I am not aware of there being any rule.
Some power pedestals, such as those used at trailer parks, actually have a light mounted on them. This might be a good idea.
I have also maintained that every panel ought to have an convenience outlet near it. I will usually install one. But again, there is no "rule" as such.
