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