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