Hi AnTTun,
I think it could be the different stocks but also maybe seasonal effect. I have found with kohyo that it grows with different colours on different stocks. I have had the same clone on Pereskiopsis, Echinicactus grusonii and Harrissia jusberti. I found that brightest colour was on the Echinocactus followed by Pereskiopsis then Harrisia. This is based on observations during summer here in the Southern hemisphere. I am wondering what the colour difference through the winter on the different stocks will be because it is generally through winter and early spring that these plants show the most red/orange/pink, they go more yellow green though the warmer months.
I have noticed that plants I have seen grafted on Myrtillocactus seem to have excellent coloration but I have not tried this stock yet. It is an interesting topic, it will be interesting to hear about other's experiences.
