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)(11,13)(12,14)(15,16)(17,18,21,23)(19,20,24,22)(25,26,30,28)(27,31,34,35)(29,32,38,36)(33,39,37,40)(1,3,5,8)(2,6,7,4)(9,11,12,15)(10,13,14,16)(17,18,21,23)(19,20,24,22)(26,28)(31,35)(32,36)(39,40)(9,10,12,14)(11,13,15,16)(17,19,21,24)(18,22,23,20)(25,27,30,34)(26,31,28,35)(29,37,38,33)(32,40,36,39)(1,3)(2,4)(5,8)(6,7)(9,10)(11,13)(12,14)(15,16)(17,19)(18,20)(21,24)(22,23)(25,28,30,26)(27,31,34,35)(29,36,38,32)(33,39,37,40)(1,4)(2,3)(5,6)(7,8)(9,11)(10,13)(12,15)(14,16)(17,20)(18,19)(21,22)(23,24)(25,29,30,38)(26,32,28,36)(27,33,34,37)(31,39,35,40)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.