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