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