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