Hi Jorge, sorry for been less active in commenting, I saw that you started to give assessment to the winners. I find it useful for me too. I remember how I did in the past using the black for black that we see on photo, and also on very dark shadow of for example a hand. But I agree with using other colours which are dark in value we can make the drawing or painting more interesting.

I think often when a child starts learning drawing and painting and adult there are two different worlds, we try to do how we see we do not want to see many other little colours in for example black or maybe better example of grey how many possibilities to create grey with other colours and not using the one from tube.

The combination of colours and contrast where we can stress one colours using the opposite one that is a master skill.

Thank you for your valuable advises.