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