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