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