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