Any strain of weed will exhibit different characteristics, or phenotype, grown under various conditions. Various conditions coud be as subtle a difference as say, growing on two different sides of your grow room. Iv'e seen clones from the same plant, show different phenotype, based on environmental conditions, and cultural practices. So two different people can grow the same strain and get way different results. The Blue in Blue Mystic, describes the Blueberry parent. They do have the potential for hues of blue, but it is based on the genetics, and most often environment. Like was said earlier, lower temps in the last stage of the plants life will often bring on the colors. Think autum. Late in the "year", or late in the plants life is when the colors change. I have grown out Blueberry and it had a tinge of blue, but the berry taste was very strong, as was the high. Good mix of head and body.