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