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