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