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