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