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