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