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