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