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