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