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