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