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