My perspective here is that many forms of fairness are inconsistent, and fall apart on significant moral introspection as you try to make your moral preferences consistent. I think the skin-color thing is one of them, which is really hard to maintain as something that you shouldn’t pay attention to, as you realize that it can’t be causally disentangled from other factors that you feel like you definitely should pay attention to (such as the person’s physical strength, or their height, or the speed at which they can run).
I think that a sensible interpretation of “is the justice system (or society in general) fair” is “does the justice system (or society) reward behaviors that are good overall, and punish behaviors that are bad overall”; in other words, can you count on society to cooperate with you rather than defect on you if you cooperate with it. If you get jailed based (in part) on your skin color, then if you have the wrong skin color (which you can’t affect), there’s an increased probability of society defecting on you regardless of whether you cooperate or defect. This means that you have an extra incentive to defect since you might get defected on anyway. This feels like a sensible thing to try to avoid.
I think that a sensible interpretation of “is the justice system (or society in general) fair” is “does the justice system (or society) reward behaviors that are good overall, and punish behaviors that are bad overall”; in other words, can you count on society to cooperate with you rather than defect on you if you cooperate with it. If you get jailed based (in part) on your skin color, then if you have the wrong skin color (which you can’t affect), there’s an increased probability of society defecting on you regardless of whether you cooperate or defect. This means that you have an extra incentive to defect since you might get defected on anyway. This feels like a sensible thing to try to avoid.