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