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