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)(12,19)(13,15)(16,20)(17,23)(18,21)(22,24)(25,26,31,34)(27,32,29,30)(28,33,37,40)(35,39,38,36)(2,6)(3,7)(9,11,13,18)(10,14,15,21)(12,17,20,24)(16,22,19,23)(25,27,31,29)(26,32,34,30)(28,35,37,38)(33,39,40,36)(1,3,5,7)(2,4,6,8)(10,15)(14,21)(16,19)(22,23)(27,29)(30,32)(35,38)(36,39)(1,4)(2,7)(3,6)(5,8)(9,10)(11,14)(12,16)(13,15)(17,22)(18,21)(19,20)(23,24)(25,28,31,37)(26,33,34,40)(27,35,29,38)(30,36,32,39)(9,11)(10,14)(12,17)(13,18)(15,21)(16,22)(19,23)(20,24)(25,29,31,27)(26,30,34,32)(28,35,37,38)(33,39,40,36)(9,12,13,20)(10,16,15,19)(11,17,18,24)(14,22,21,23)(25,30)(26,27)(28,36)(29,34)(31,32)(33,35)(37,39)(38,40)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.