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