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