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