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