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