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