How do you apologize to someone who seems like they are still mad?

Because they are still mad doesn't mean to say you can't apologise [i]if[/i] you think you said something out of order. It could be said the sooner you try to make amends the better you might appear to them; whilst it should be said that, sometimes, an apology might be hard for some to accept until things cool down. But in any event, you making the first, and quickest, attempt to put things to rights can never be said to be a bad thing.