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