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