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