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