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