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