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