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)(28,36)(29,39)(30,32)(31,37)(33,38)(35,40) 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)(26,31)(28,35)(29,36)(30,37)(32,34)(33,40)(38,39)(1,3,5,4)(2,6,7,8)(10,14)(15,22)(16,19)(23,24)(26,32)(28,38)(31,34)(35,39)(9,10)(11,15)(12,16)(13,14)(17,23)(18,22)(19,21)(20,24)(25,28,30,38)(26,33,32,36)(27,35,37,39)(29,31,40,34)(1,2)(3,6)(4,8)(5,7)(9,11,13,18)(10,15,14,22)(12,20,21,17)(16,24,19,23)(25,27)(26,34)(28,35)(29,33)(30,37)(31,32)(36,40)(38,39)(1,4,5,3)(2,6,7,8)(9,12)(10,16)(11,17)(13,21)(14,19)(15,23)(18,20)(22,24)(25,29)(26,35)(27,36)(28,31)(30,40)(32,39)(33,37)(34,38)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.