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