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