If you have effects on a color channel, you can monitor an input through that color channel. To monitor through a color:
Show Loopy Pro's mixer.
Tap on the icon at the top of the channel that you want to monitor
Tap on the speaker icon to turn off monitoring through the mains
Tap on the icon (which will probably say No Color) that brings up the color picker.
Choose the Color whose Effects you want to monitor through.