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