green background helped me to get true color of flowers

Hello,
I have purchased two new phals yesterday - purple and yellow. I spent whole day today trying to make good pictures of them, but had trouble with getting true color of flowers.
I experimented with different backgrounds, lights etc. with no luck.
At the end I put them in front of my big old ponytail palm and that was it - they started to come up with right color under any light.
I have attached the pictures resized to 30% of actual size.
What do you think?