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