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