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)(16,20)(17,24)(18,23)(19,22)(21,27)(26,28) involution — undirected(5,6,8,9)(7,11,12,10)(13,15,17,27,18,16,19,26)(14,20,24,28,23,25,22,21)(13,16,18,15)(14,21,23,28)(17,27,19,26)(20,24,25,22)(2,4)(5,7,8,12)(6,10,9,11)(13,17,18,19)(14,22,23,24)(15,26,16,27)(20,28,25,21)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.