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