One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,7)(3,5,8,6)(10,15)(11,19)(12,23)(13,26)(16,30)(17,32)(18,24)(20,36)(21,38)(22,35)(27,29)(28,31)(33,37)(34,39)(9,10,14,18)(11,20,22,16)(12,24,23,15)(13,27,26,17)(19,33,35,31)(21,28,39,37)(25,29,40,32)(30,38,36,34)(2,5)(3,8)(6,7)(9,11,12,21,14,22,23,39)(10,16,15,28,18,20,24,37)(13,19,25,34,26,35,40,38)(17,31,29,30,27,33,32,36)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.