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