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