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