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