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