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)(15,26)(16,28)(17,22)(18,23)(19,24)(20,25)(21,27) involution — undirected(1,2,3,4)(7,8)(10,12)(13,15,19,16,20,22,18,27)(14,21,23,17,25,28,24,26)(5,7,9,8)(6,10,11,12)(13,16,19,22,20,27,18,15)(14,17,23,28,25,26,24,21)(5,8,9,7)(6,10,11,12)(13,17,20,26)(14,22,25,15)(16,23,27,24)(18,21,19,28)(13,18,20,19)(14,23,25,24)(15,27,22,16)(17,28,26,21)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.