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