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