I have had my cactus for a few years now and throughout it has been cared for and neglected, during tons of moves and whatnot. It seems to be growing at an alarming rate at the top, the needles are white and it's a beautiful green. However, a majority of the bottom half is a concerning color. The bases are really strong in the soil but if I brush against the needles, they fall off. I do not fertilize it or change the soil. I have attached an image for a better visual.
Spine colour can change in response to a change in growing conditions (on some species), and they often do so as they grow older as well. I do agree with the previous post, they do look as if they have grown in too low light.
