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