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