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