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