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