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