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