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