hey mate, lophs go red like that from sunburn. That one is still quite small, did you recently transfer it from the seedling tray to direct sun? They require hardening off from the humid seedling stage and gradually being introduced to harsher conditions.
I'd generally go for a higher mineral content in the substrate, but that mix should work. When you say 1 part cactus soil, do you mean the stuff you buy at bunnings? I would advise against buying any soil from bunnings in general, there is better value elsewhere and bunnings ones are heavy on the composted pine cause it's cheap but you end up with poor quality acidic soil, they're usually infested with fungus gnats too.
Lophs would like a substrate that's slightly on the alkaline side. If it was me I would sprinkle some gypsum around the loph to slowly be watered in over time. Or I'd put some in the container that you bottom water with.
Most likely more experienced growers will offer better advice, but if it was me, I would give it more shade until it's bigger and hardened off to the sun. In nature they are commonly shaded under trees or in crevices. I personally wouldn't transplant it to new substrate because I think it damages the root, affecting growth rate and exposing it to diseases.
I reckon it will be fine though