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