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