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)(27,30)(28,31)(29,32)(33,36)(34,38)(35,39)(37,40)(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)(26,30)(28,35)(29,34)(31,39)(32,38)(33,37)(36,40)(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)(27,34)(28,36)(30,37)(32,33)(38,39)(2,5)(6,8)(9,11,14,13)(10,15,17,18)(12,19,22,21)(16,23,20,24)(26,32)(30,38)(31,33)(37,39)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.