Yellow Cacti ID help please

Hi all,
Sorry to keep clogging up the forum with ID requests, But I have two weird cacti and I was wondering if someone had an explanation for their yellow colour/ an ID for them?

Thanks, TC

This little guy is a yellow colour, he's been like this since I got him as a seedling,...



This one is more of a limey green, again hasn't changed since a seedling.

Top one echinopsis maybe. Bottom one looks like a rebutia I have. Top also looks like full variegation. (The same trait that all those candy coloured gymno's show.) Is it very slow growing?

I was thinking Echinopsis as well Sneaky.

It's more of a lime green/yellow than that pic shows, I'll get a better photo using my camera rather than my phone on sunday. I was thinking full variegation, but I wasn't sure if that was a thing. I've only had it for 6 months, but haven't seen any growth in that time at all.

TC, the lack of chlorophyll is not so seldom. If chlorophyll is absent, the normal sun blockers appear.
In most cases yellow or red.
Many hybrids have this trait.  

That's interesting Torro, I've seen full variegation on grafted cacti (yours are really beautiful by the way   ) but I have never seen one growing on it's own.

I've heard of (but not tried myself) yellow and purple Gymnocalycium mihanovichii being able to survive and grow on their own roots, but growing very slowly because they have only some chlorophyll, while the red ones have so little that they die.

On a side note, does anyone know if you can induce variegation by limiting the amount of magnesium the plants get?

I have a number of very red, unidentified gymno's that only develop a slight green color during the wet season. They survive fine on their own roots but are very very slow growing. I think it would be possible to induce colour change by influencing minerals in the soil but you would have to be careful to not induce a fatal deficiency.

Wet season (3 months)


Every other time of the year

They don"t like the sun. Have you got them in a hot spot?