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