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