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