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