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