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