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