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