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