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