Good pictures above^.
It may take a little getting used to but its mostly about the arrangement of the spots/stripes to tell the difference. The body shape though is also an indicator sometimes. The motag is a little different usually than the other two, which helps differentiate it from a freddy (since barring colour, their patterns look fairly similar to a beginner). You can tell a fairly distinct difference in female loisellei pattern when compared to Motaguense and Freidrichsthalli.
Good luck,
Chris