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