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