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