When connecting a battery with red and black wires, the black wire is typically the negative one, according to Pep Boys. The red wire is usually the positive.
According to Pep Boys, connection terminals at both ends must be checked before making a connection. Even more important than the color of wires are the actual connections themselves. Regardless of the wire colors, the positive terminal should be marked with a "+" symbol. Reversing the connection by hooking positive to negative can cause a reverse in polarity, damaging the battery or the system that is being connected. Reversing the polarity may create a shock hazard.