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)(25,26,31,29,30,33,28,39)(27,34,37,40,38,32,35,36)(1,3,4,7)(2,5,6,8)(9,11)(10,15)(12,19)(13,21)(14,20)(16,23)(17,18)(22,24)(25,27,30,38)(26,32,33,34)(28,35,31,37)(29,36,39,40)(2,6)(3,7)(9,12,14,13)(10,16,17,22)(11,19,20,21)(15,23,18,24)(25,28,30,31)(26,29,33,39)(27,35,38,37)(32,36,34,40)(2,6)(5,8)(11,20)(15,18)(19,21)(23,24)(25,29,31,33,30,39,28,26)(27,36,37,34,38,40,35,32)(9,13,14,12)(10,16,17,22)(11,21,20,19)(15,23,18,24)(25,28,30,31)(26,29,33,39)(27,37,38,35)(32,40,34,36)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.