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