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