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