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