I started off by selecting a fruit. I looked at various options and felt that your example including a leaf really did give the most interesting possibilities. I chose a pomelo, but really it's the same shape as a pear. I made two templates to start with but ended up making a third smaller template to complete one of the extra activities. I used acrylic paints throughout and used the same primary colour bases: cerulean, cadmium yellow and alizarin crimson.
I chose Cadmium yellow and violet as my first two complementary colours. I thought this was a marvelous combination
Then I chose Cerulean blue and Orange:
Then red (Alizarin Crimson) and green:
I then moved on to using two secondary colours, green/yellow and red/violet. This picture may not have come out as clearly as I would have liked, or it could be that the red/violet had quite a strong effect on the green/yellow.
Finally in this activity I mixed two complementary tints: blue/green and red/orange.
I had to drag myself away at this point otherwise I would have gone on forever on this exercise.