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