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