Can somebody help me?

i 've this cactus at home in the same position for 4 years

i've see a strange color and i have routate it.
i've see this:



can somebody help me?

maybe the cold winter is the cause?

(sorry for my english)

Ok - I try to help you. :)

I think this is Euphorbia tetragona. This isn't cactus - this is succulent ;) Maybe cold winter is the cause, because temperatures for this plant must be upper than 12 degrees C.

and they like lots of sun

ok..thx.

today i ve try to repot and do some cutting.

the temperature is always over 12