Study value

Recently i joined another drawing course again last year, this one is the task they tell me to do. I kinda still don't understand value or color, I think I need to draw more something like this....

reference:

Our lecturer just told us to do distortion version and cartoon-y face based on reference, reference only used for color pick. I gladly doing some mean girls face :D (I love bitchy sass face ok, maybe that why I like some villain character, they bring greatest expression than the protagonist XD)