The plant usually flowers in dark pink. I found the light pink form at an incidence of roughly 1:100,000 plants during my Fairbanks trip. (Very rough estimation from observed density in an open field where this photo was taken.) I saw one small patch of just the lighter shade, but it was along the highway where I was not able to stop and take photos.
I had hoped to gather seeds for my garden, but none were to be found during my trip. The seeds mature well after all the flowers have withered away, so I would have to plan a trip later in the season if I want to find any. Since the light-colored form of the plant would look no different from all the others, I'd have only the slightest chance of getting seeds for this novel form.
My research indicates Fireweed can also be found in my home state of Minnesota. I'd never noticed it before, but since I've seen it up close recently... I've now noticed a few isolated patches of what looks like a smaller version of the Fireweed I saw in Fairbanks. Unfortunately, the patches were along highway margins, so I didn't have the opportunity to examine the plants in detail.