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