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