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