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