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