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