Connect the red wire to the R terminal on the t-stat, connect the white wire to the W terminal, connect the green wire to the G terminal and connect the blue wire to the Y terminal on the t-stat. The B terminal is not used on most thermostats. Unfortunately most manufacturers of thermostat wire do not make 4-wire with a yellow wire and instead make it with a blue wire, that is why they don't match up perfectly. The red wire provides 24v power from the furnace, the white wire controls the call for heat from the t-stat, the green wire controls the fan, and the blue wire/yellow terminal controls the air conditioner.
