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