White leafed Begonias?

[NewSunRay]

I have found some Begonias which appear whited leaved in pics in online stores. However, often they take a mint green or light violet appearance in person. I understand there are certain conditions which can be employed to make these types of Begonias appear whiter of leaves. So what kind of conditions, whether temperature, light, humidity, or otherwise will encourage a lighter leaf? Of these three factors, which should be higher, and which lower, and which within a certain range, for this purpose?

Also, one of the sellers I purchase from, informed me that they do not grow the very white leafed varieties, due to their great sensitivity. I would appreciate if someone would give me examples of this kind of species.

Thanks in advance!