Furnace blower will not start

I have a Rheem Criterion II furnace with a White Rodgers 50M56-843 control board. Blower runs in manual ON or COOL mode, but will not start when needed for heat. Exhaust blower starts, burners ignite and burn until shut down due to over temp condition. The control board was replaced in the summer when the original board failed. Not certain the blower wires were installed correctly or if the heat mode was tested then. I have Black to Cool, Red to Lo Heat, Blue and Yellow are parked. Hi Heat has nothing connected. I am unable to find a color code that describes the functions of the blower leads. This is a single stage unit with a constant speed fan. Instructions for the control board say that one of the parked wires should be connected to Lo Heat for constant speed. That's confusing given the way it is currently wired. Looking to verify the blower connections, and if they are correct, what I should check next. Thanks.