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