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