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