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