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