A speaker's wire plugs are generally red (positive) and black (negative). Red wires connect to red plugs, and black wires connect to black plugs. If a speaker's wires contain different colors, the wires should be matched to their plugs by their positive and negative symbols.
Speaker wires must be connected to their correct speaker plugs, also called terminals, or the speakers won't work. Some speakers have four terminals each, and some only have two. The key to connecting the wires properly is to remember to match positive wires with positive terminals and negative wires with negative terminals, meaning red wire to red terminal and black wire to black terminal.