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