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