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