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