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