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