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