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