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