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