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