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