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