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