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