We will start by painting the trunk of our gum tree.
The initial watercolors I use are French Ultramarine with a touch of Alizarin Crimson (this purplish mixture should still lean towards the blue), Burnt Sienna and Cadmium Orange.
The colors are very weak at this stage, like chinese tea. The Cad Orange, especially must be kept very weak or it will become opaque.
Gum tree trunk under painting
Start by laying down the first wash with the purple. Using quick strokes leave part of the paper unpainted. The majority of the unpainted surface should be towards the light as these will become part of the highlights.
While the purple is still very wet, drop in the Burnt Sienna on the side of the tree away from the light and the very weak Cad Orange on the side towards the light. Preferably don’t paint over all the white paper on the trunk if you want to keep some strong highlights.