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