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)(27,36,39,28)(30,34,40,35)(32,33,37,38)(1,3,5,4)(2,6,8,7)(9,11)(10,14)(12,18)(13,17)(15,21)(16,20)(19,23)(22,24)(25,27,30,38,31,39,40,33)(26,32,35,36,29,37,34,28)(1,3,5,4)(2,7,8,6)(10,15)(11,17)(16,22)(18,23)(25,28,40,37,31,36,30,32)(26,33,34,39,29,38,35,27)(1,4,5,3)(2,6,8,7)(12,19)(16,22)(18,23)(20,24)(25,29,31,26)(27,37,39,32)(28,33,36,38)(30,34,40,35)(9,12,13,19)(10,16,15,22)(11,18,17,23)(14,20,21,24)(25,30,31,40)(26,34,29,35)(27,33,39,38)(28,32,36,37)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.