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)(15,23)(16,20)(17,21)(18,27)(19,25)(22,24)(26,28) involution — undirected(1,2,4,3)(5,6)(7,10)(8,9)(11,12)(13,15,17,25)(14,19,21,23)(16,18,26,24)(20,22,28,27)(6,9)(10,11)(13,15,24,26,17,25,18,16)(14,20,27,19,21,28,22,23)(5,7,8,12)(6,10,9,11)(13,16,18,25,17,26,24,15)(14,19,22,20,21,23,27,28)(1,3,4,2)(14,21)(19,23)(20,28)(22,27)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.