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