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