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