I've never heard of such a thing, but I took a look at some of my Siberian seedlings, and two of them are very light in color. On the larger one, I can see some green on the edge as if it were variegated. At first, I thought the light color was due to the fact that they started germinating in the dark, but when I moved them to the sun, the other two greened up. And now, there's a fourth one coming up that's light like the first one and it has been in sun the entire time. Do some Siberians maybe have light foliage? I've never seen that, but I also don't pay that much attention to Siberians.