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