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