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