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