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