Thank you all for nice comments!
The dark one is from latest Thai breeding. And yes, the backside of the petals is white with some red speckles at the border. It looks like a reverse picture of the front site. You can see this clearly at the second flower of the dark one that is shown at the photo between the two flowers.
All my line-breed godefroyae seem to need more water than the more wild-type ones. I grow these in pure Orchiata and they like to be watered frequently, while the wild-type godefroyae grow well in a mix of Orchiata and limestone.