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