The scan is very deceptive with this photo.
I used a triad, Sennelier Blue Indanthere (PB60), and Winsor Newton Permanent Rose (PV19 & Lemon Yellow (PY53), for the painting and the background was a wet on wet mix of the Blue Indanthrene and Permanent Rose.
In the scan, the Blue Indanthrene is much more predominant, whereas in real life the mix is more violet throughout. It makes the flower values look uneven as well. I tried fixing it with Picasa, but couldn't make it work. Ah well.