Drawing BIG thumb
Ready to mix the color
Pure green
Starting to pain the apple
Green mix with yellow, orange, brown...
Try the color
Pain at the place in correct
Adding stroke and shadow
Adding highlight
The "stem"
Starting to pain the background
Remember don't make the color too watery

Make the apple more 3D
The highlight is not enough, so add the pure white for the highlight, and done.
This is another reference that lecture drew and paste on the wall.