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