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