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