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