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