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