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