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)(14,18)(15,20)(16,24)(17,29)(22,37)(23,33)(25,32)(27,40)(28,36)(30,35)(31,39)(34,38) involution — undirected(1,2,4,5)(3,7,8,6)(9,11)(10,16)(12,27)(13,23)(14,24)(15,25)(17,34)(18,32)(19,21)(20,33)(22,28)(26,31)(29,39)(30,38)(35,37)(36,40)(9,12)(10,17)(11,22)(13,29)(14,28)(15,30)(16,31)(18,26)(19,35)(20,36)(21,34)(23,27)(24,38)(25,39)(32,40)(33,37) involution — undirected(1,3,4,8)(2,6,5,7)(11,23)(13,14)(16,32)(18,19)(21,33)(22,27)(24,25)(26,35)(28,29)(31,40)(34,37)(38,39)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.