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