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