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