I`m going to be painting from this almost as it is, nothing much to change, maybe add a bud or two; the composition looks fine as it is.
The colors that I have chosen for now are Schminke`s ruby red, DS new gamboge (because the yellow on the left flower is actually the tertiary color yellow orange and not a pure yellow) and MG phthalo blue. Here is the lower petal of the left most flower. I have already added the small shadows at the bottom of the petal in this first wet in wet wash.
Here I have added the cast shadow with a mix of the red and blue plus a little yellow to dull down the resulting violet.