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