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