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