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