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)(25,26,30,36)(27,34,28,32)(29,35,31,33)(37,40,38,39)(1,2)(3,7)(4,5)(6,8)(9,11)(10,14)(12,18)(13,19)(15,21)(16,17)(20,24)(22,23)(25,27)(26,32)(28,30)(29,38)(31,37)(33,39)(34,36)(35,40) involution — undirected(2,5)(6,7)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(26,33)(29,31)(32,39)(34,40)(35,36)(37,38)(10,16)(14,17)(15,22)(21,23)(25,28,30,27)(26,34,36,32)(29,37,31,38)(33,40,35,39)(1,3,4,8)(2,6,5,7)(11,19)(14,17)(18,24)(21,23)(25,29,30,31)(26,35,36,33)(27,37,28,38)(32,39,34,40)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.