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