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