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