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