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