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