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