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