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