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