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