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