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)(11,18)(12,17)(13,15)(14,19)(16,21)(20,23)(22,24)(26,30)(27,33)(32,37)(35,38)(1,3,5,8)(2,6,7,4)(9,11)(10,14)(12,19)(13,20)(15,22)(16,23)(17,18)(21,24)(25,26,28,30)(27,34,33,40)(29,37,36,32)(31,38,39,35)(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)(11,19)(13,21)(14,22)(15,17)(18,23)(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.