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