This is my latest Watercolor Painting. I love painting roses, however, yellow roses are challenging because of the shadows.   Always reach for the opposite color on the color wheel when painting shadows.   In this floral I used a mixture of Violet and red to deal with the many shadow areas.  Use watercolor paper scraps to test your colors. You can make yellow swatches and then try different shadow colors until you find the right one. The yellow pigments are important also. I like Deep Yellow, but if I had chosen a different pigment--- such as Naples yellow, my shadow color would be different.  When ever possible I use transparent colors for best results. Botanical painting is often composed of many layers of paint. If you choose opaque color you can easily create a muddy look!     I hope this is helpful to all you paintings!!