5 and 6 year olds.
I've been given a selection of little acrylic paint tubes. There are only five colours, but limiting the options is not a bad thing.
I gave the children a little demonstration on how to use the paints to create new colours, using a lid as a pallet. They only used a pea sized blob of paint at a time. They drew 5 squares on a page. The idea was to mix a new colour and paint a square. Then give it a name. They were very focussed and created some excellent colours and names.
I showed them a photo of a hillside full of old houses in Wellington. We discussed how they appeared to be on top of one another. I showed them how to draw the bottom house first, then to add what they could see of the houses above. They understood this concept very easily and went on to fill their page with houses tumbling down a hill.
Using their new paint mixing skills, they painted their houses.