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