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