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