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