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)(12,23,25,35)(13,26,28,40)(15,31,30,19)(17,33,34,29)(21,37,27,38)(24,36,39,32)(1,3,5,4)(2,6,8,7)(9,11,14,22)(10,16,18,20)(12,15,25,30)(13,27,28,21)(17,32,34,36)(19,35,31,23)(24,33,39,29)(26,37,40,38)(9,12,15,22,14,25,30,11)(10,16,19,23,18,20,31,35)(13,24,29,27,28,39,33,21)(17,32,26,38,34,36,40,37)(9,13,15,29,14,28,30,33)(10,17,19,26,18,34,31,40)(11,21,12,24,22,27,25,39)(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)(26,40)(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.