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