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