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)(15,19)(16,22)(17,21)(18,24)(20,23)(25,26)(27,28) involution — undirected(2,4)(13,15,19,14)(16,25,17,27)(18,24,20,23)(21,26,22,28)(6,9)(10,12)(13,16,18,28,19,17,20,26)(14,21,24,25,15,22,23,27)(13,17,20,28,19,16,18,26)(14,22,23,25,15,21,24,27)(5,7,8,11)(6,10,9,12)(13,18,19,20)(14,23,15,24)(16,26,17,28)(21,25,22,27)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.