The starters group (Avril and Fabienne) is working on spheres, a very important excercise for understanding and suggesting 'volume'. Using highlights, consistent shadows - not always evident - and the right colour combinations.
It is a nice one to work on, and sometimes a more experienced watercolorist participates too, like Christine, because it is so much fun. One of the subjects is 'complementary colours'
If you use the complementary colour as the shadow colour, the effect is 'warmer' than when you use black, blue or grey...
The direction of the shadow that the object itsel makes on the surface should be consistent with the direction of the light, which can be derived from where the highlight is... It's not that easy actually, there's a lot to be puzzled about, and I think the group did a good job!!
If you too want to know about these kind of things, come to the watercolour class. The starters exercises are fun and give you a basic understanding of the technique but also of colour use and characteristics...