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