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)(15,22)(16,17)(18,21)(19,27)(20,24)(23,28)(25,26) involution — undirected(5,6,9,10)(7,11,8,12)(13,15,17,23,18,24,19,25)(14,20,16,26,21,22,27,28)(5,7)(6,11)(8,9)(10,12)(13,16,17,14,18,27,19,21)(15,20,23,28,24,22,25,26)(2,4)(5,8,9,7)(6,12,10,11)(13,17,18,19)(14,16,21,27)(15,23,24,25)(20,26,22,28)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.