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