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