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