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