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