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