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