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