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