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