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