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