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