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