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