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