Basically the bulk of krypton was turned into green k. Most of the other varieties are said to be isotopes of green k.
Fun bit of info, that!
The standard explanation for Red Kryptonite is that as some ordinary Green K meteorites are flying through space, presumably on their way to earth (to which they seem inexorably drawn), they pass through a cloud of space dust of vague origins that gives them not only a handsome new colour but also changes their properties somehow. As for the others, like Gold K and White K, I don't even know if they've been given origin stories, except for Blue K, which is just ordinary Kryptonite that has been subjected to the Bizarro treatment.
Blue k was never green k. Kal created it with the imperfect duplicater ray that created Bizarro. White k & red k were said to have been green k that had flown through "cosmic clouds". A white cloud in white k's case. In red k's, a red cloud. Makes me think about the "cosmic cloud" that gave Johnny Kirk kryptonian powers. Could those different "cosmic clouds" have been the same one? Maybe even a living entity? Considering that krypton was so much larger than earth, all the kryptonite that reached earth is probably only a tiny fraction of the total amount in the universe.