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