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