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