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