Could these possibly be cobalt blue zebras? They came with my new tank, and the seller said they were cobalt blue zebras. They're 2-2.5" long. About a week after I got them, the stripes appeared and two started turning yellowish while three remained blue. I assumed it was stress, but the color changes have stuck. Now a little over a month in, the blue ones are getting yellow on the tips of their fins. Did I get ice zebras instead? That would be an upgrade to me, but I am still stumped by the yellow ones then.