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