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