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