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