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