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