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