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