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