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