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