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