Ripe pomelos' peel is light green, and once it turns pale yellow, they are ripe enough to be consumed. Be sure to pick pomelos with triangular shape, as this is an indicator of juiciness. 

How to tell if Ripe:

Green = Unripe
Yellow = Ripe

Next, look out for bumps on the peel: if the peel is smooth and shiny, the fruit is not yet ripe, and it is best to wait before eating it.

If the peel is wrinkled and is not very smooth, you know it is ready to eat.