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