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