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