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