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)(31,37)(35,40)(38,39)(9,11,14,20)(10,15,17,24)(12,19,13,22)(16,23,21,18)(25,27,30,38)(26,31,32,40)(28,37,29,35)(33,36,34,39)(9,12,14,13)(10,16,17,21)(11,19,20,22)(15,23,24,18)(26,32)(31,40)(33,34)(36,39)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.