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