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