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