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