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