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