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