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