Is Light Needed To Add Toning?

Yes that will work. Actually many items will make coins tone. Placing a coin in a box, bag, jar with ground up match heads will work fine. Same with parts of eggs but that gets mushy and smelly. Same with many items found around the house.
If you use the Search tab at the top and type in Toning, Toned coins, etc. you should find many posts about that subject and many possible methods of toning.
Remember that toning on a coin is in a way similar or the same as tarnishing, corroding, staining, etc. It is a chemical reaction of the coin's metal with a substance usually in a gasseous form. Some solutions too will create that toning effect. Gun Bluing solutions are an example.
The Sun does little to tone a coin unless the coin is within a few miles of the Sun of course. Light does nothing to metals but the Infra Red portions of light are actually heat and that will increase chemical reactions such as coin toning. No one so far has proven that cosmic rays from space tones coins though. Most portions of visible light will just bounce off metals but there are numerous parts of light that are not visable such as the Infra Red bands and those would effect metals as noted above.
For toning coins there are so many methods attempted all the time that it is really becoming difficult to know what is AT and what is NT. That debate has been discussed here many times too.

The mechanism for toning is well documented in the book Coin Chemistry. I suggest you buy a copy, it's a great reference book. In a nutshell, toning is simply the reaction of hydrogen sulfide and a metal. Light has nothing to do with the process.

And also the angle that the coin is photographed

That's true Carl, but the main culprit is H2S....I was trying to use the KISS program. LOL