The signal style is set by using the Signal Style setting in the indicator's settings dialog. Setting this to All will highlight every candle that matches the TrendMaster entry/exit criteria. These candles are then coloured green or red depending on the type of signal.
Changing this setting to Only start of trend means only signals that are preceded by an invalidated signal are shown, signalling that a new trend is forming. Here's an example of that same chart with the Only start of trend signal mode enabled.