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