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