Also when I was younger(and now still tbh) I watched Love2DrawManga on YT, her videos are really good and did one on lighting!
-Reflect light(or whatever it is), like the bright colour of your shirt bouncing off and hitting under your face.
-Colour of the lighting is dependent on the environment and/or mood.
-White manga lighting(like in old manga covers), once a source is chosen, just use white for the light.

( @LYCAN)

Not sure if this helps, I don't really pay attention when I colour.