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