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