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