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