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