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