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