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