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