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