The standard build in Hero 6th, at least everywhere I've encountered it including Champions Powers, is the Images build:
Game Information: Images to Sight Group, +4
to PER Rolls, Area Of Effect (16m Radius; +¾)
(38 Active Points); Only To Create Light (-1).
Total cost: 19 points.
Which, fine, sure, it gets the job done but sure feels like an "official kludge" to me. GURPS ran up against a similar thing, with people trying to argue over how much energy you needed to Create with the Create power to generate enough light to see by. So they did an official kludge as well and made it a one-point perk.
My gut definitely says it should be a Change Environment power for all the reasons folks have listed above, and it was at least as far back as 4th edition, though to be fair Change Environment was super loosey-goosey back then.
A character with this Standard Power can cause minor
changes in the environment. The character could, for
example, create light in a certain area, change the temperature,
or set up an intense (but non-damaging) magnetic field.
Change Environment cannot be used to duplicate existing
effects (like Darkness); moreover, it does not have any direct
effect on combat. However, Change Environment can be
used to affect Power Limitations or character Disadvantages
like Susceptibilities. At the GM’s option, Change Environment
can have a slight effect on combat (small minuses to
PER Rolls, OCVs, etc.), according to the special effect and
the exact circumstances.
Clear as mud, and essentially boiling down to "ask your GM..."