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