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