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