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