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