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