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