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