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