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