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