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