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