The default settings are the same. The alerts are based on the long and short signals that occur upon a cross of the momentum line to the positive or negative respectively.
Green background is bullish, red is bearish. Bright green lines indicate a long signal, bright red a short signal.
White background means no trade since we are in a period of choppy/sideways price action.
It can be useful to use momentum as a divergence indicator against price as an aside.