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