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