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