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