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