Painting Shadows on Flower
Starting at the top left hand section of the flower, start putting in the shadow areas with a mix of Cobalt Blue and Burnt Sienna. This will create form in your flower through the various cast and form shadows that appear. Keep an eye on tones here to make sure you do not go too strong in the peripheral areas. The strongest tones  of the flower will be near the centre of the flower which is also the focal point of the painting. Ensure you leave the non-shadow areas white when you do this step of the painting.