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