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)(11,13)(12,20)(14,15)(16,18)(17,21)(19,24)(22,23)(27,33)(31,34)(35,39)(38,40)(1,3,4,7)(2,5,6,8)(10,15)(12,21)(13,16)(19,22)(25,26)(27,31)(28,36)(29,30)(32,37)(33,34)(35,40)(38,39)(1,2)(3,5)(4,6)(7,8)(10,15)(11,18)(17,20)(19,22)(26,30)(31,34)(32,36)(38,40) involution — undirected(9,11,14,18)(10,16,15,13)(12,22,21,19)(17,23,20,24)(25,26)(27,34)(28,32)(29,30)(31,33)(35,40)(36,37)(38,39)(1,3)(2,5)(4,7)(6,8)(9,12,14,21)(10,17,15,20)(11,19,18,22)(13,23,16,24)(25,27,29,33)(26,31,30,34)(28,35,37,39)(32,38,36,40)(1,2)(3,5)(4,6)(7,8)(9,13,14,16)(10,18,15,11)(12,23,21,24)(17,22,20,19)(25,28)(26,32)(27,35)(29,37)(30,36)(31,38)(33,39)(34,40)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.