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