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