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)(11,12)(13,15)(14,16)(17,18,20,22)(19,21,23,24)(25,26)(27,34)(28,32)(29,33)(30,31)(35,40)(36,37)(38,39)(9,11,14,13)(10,12,16,15)(19,23)(21,24)(26,31)(27,32)(33,39)(35,37)(1,3,6,5)(2,7,4,8)(9,11,14,13)(10,15,16,12)(17,19)(18,21)(20,23)(22,24)(25,27)(26,28)(29,37)(30,32)(31,34)(33,40)(35,38)(36,39)(1,4,6,2)(3,7,5,8)(9,12,14,15)(10,11,16,13)(25,28)(26,32)(27,31)(29,36)(30,34)(33,37)(35,39)(38,40)(1,5,6,3)(2,7,4,8)(9,13,14,11)(10,15,16,12)(17,18)(19,21)(20,22)(23,24)(25,29,30,38)(26,33,31,39)(27,35,32,37)(28,36,34,40)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.