One vertex per element, one color per generator, with an edge from x to x·s.
(2,4)(5,6,7,8)(10,17)(11,23)(12,14)(13,15)(18,33)(19,20)(21,31)(22,32)(24,35)(25,38)(27,30)(28,29)(34,36)(37,39)(1,2,3,4)(9,10,14,20,15,21,29,32,16,22,28,31,13,19,12,17)(11,24,26,35,23,33,38,36,27,39,40,37,30,34,25,18)(9,11,13,23,16,27,15,30)(10,18,19,35,22,36,21,37)(12,26,28,38,29,40,14,25)(17,24,31,33,32,39,20,34)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.