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