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