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)(13,14,17,18)(15,19,23,21)(16,20,26,25)(22,27,28,24)(6,9)(7,11)(13,15)(14,19)(16,24)(17,23)(18,21)(20,22)(25,28)(26,27) involution — undirected(2,4)(5,7,8,11)(6,10,9,12)(14,18)(15,21)(19,23)(20,25)(22,24)(27,28)(6,9)(10,12)(13,14,17,18)(15,19,23,21)(16,25,26,20)(22,24,28,27)(13,16,17,26)(14,20,18,25)(15,22,23,28)(19,27,21,24)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.