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