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