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