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