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