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