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