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