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