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