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