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