very yellow cactus

[Ouch]

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Apart from being very yellow, it seems fine. No soft bits and the new tiny offset in the centre is green. It's been like this for months. It is outside in all weather and is currently enjoying a very sunny and warm summer. I have another one, different variety which is very green and well. I am perplexed so any ideas would be great.
p.s. I know there is another forum for this but can anyone has it a guess as to what variety it is?

[kristian_Fossmo]

The yellow colouring shows the lack of chlorophyll, either lack of nutrient to synthesis it (mostly Fe, Mg or NO3-), but those unsufficiencies usually shows in the new growth, which in your case is green?? wierd..., or the inability to synthesis it do to genetics. It´s the carotenoids (helper pigments) that gives it the yellow colour.