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