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