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