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