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