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