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