Hi Koso, and welcome.
You have not said what kind of lighting this has been getting, but it appears to have too much. The dark and reddish coloration is almost always from lighting that is too harsh.
I see it is in a pot with another cactus, which needs the bright light. I would suggest putting your yearling in a separate pot for starters.
Prep the pot with a sand/ loam/ small gravel mix, with a bit of lime like crushed oyster shell. Use a teaspoon to remove the small cactus, going deep to not harm the developing tap root, and transplant, soil and all into the new pot. You can then settle it in with a light watering.
I do not know if you use artificial or natural light. I am in a warm climate so I use natural, and yearling yotes do best with some morning sun, and then broken shade for the rest of the day. This one should show some color improvement in two to three weeks of indirect bright light or only some morning sun.
More details on the growing conditions would help us be more precise, but the pictures were a big help.