Answer to Colorful Crime

The bank robber was wearing a blue hat. Say Jake is the liar and Joe is the truth-teller. That means Jake actually did say that the robber was wearing a red hat. But whatever Jake says is false, so the robber's hat was blue.

Now let's say that Joe is the liar and Jake is the truth-teller. That means that Jake really told his friends that the robber was wearing a blue hat. And since Jake always tells the truth, the robber's hat was, indeed blue. The answer is blue — either way.