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