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