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