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