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