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