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