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