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