If you say that someone's face is red, you mean that it is redder than its normal colour, because they are embarrassed, angry, or out of breath.

You describe someone's hair as red when it is between red and brown in colour.

Something that is red is the colour of blood or fire.

You can refer to red wine as red.

If a person or company is in the red or if their bank account is in the red, they have spent more money than they have in their account and therefore they owe money to the bank.

If you see red, you suddenly become very angry.