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