As was noted earlier, there will be some sellers (Master Lock is one of them) that will randomly select a color for your lock. For consumers, this can be a little bit frustrating as it seems like a pointless limitation to have. But, it does make sense.
Master Lock personally addressed this question and made mention of the fact that they ship all their colors (talking about one of their models) under the same SKU number. To then process the original colors would not be cost-effective for them.