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