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