This is the first layer of very light color. The main purpose of this layer is to add color to the flowers.
This is how it looked at the end after adding color and value to the flowers (I still need to paint the little curly things on the front of the top left orchid...).
I mixed a brown with the 3 primaries (red, yellow, and blue) using more yellow and red in the mixture so it becomes brown. I wet the background and then dropped in the color. I also dotted it with blue (you can add blue or another color if you feel so inclined). We now have the underpainting done (except I still need to paint the little curly things on the front of the top left orchid, I keep forgetting).