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